Mayang's Free Textures is an excellent website full of texture images which can be downloaded. http://www.mayang.com/textures/Architectural/html/Brick/index.html
This is an example of the bricks texture page.
I scroll down to find the brick surface I want to use and click, bringing up the full image. For this example, I chose a random, irregular brick with lots of varying colors. For a more regular brick, it is a lot less work, or maybe more, depending on your point of view.
Before downloading it, however, I open my graphics program (PaintShopPro) and click on File in the taskbar at the top of the screen for a New Page, 8 1/2 x 11, but at 300 pixels. Once I have my full sheet of bricks made, I can reduce to the size I need without losing clarity.
Then I click on View Grid in the taskbar. This will slightly blur what I see, but it allows for accurate placement of images.
Then I return to my internet site and right-click to Save Picture As ...
and then save it to an appropriate file and then open it in my paint program. Or, I can Copy it (Control C) and Paste it (Control V) as a New Image, then save it as Gray London Bricks Original. Because I do not want to work with my original, I make a copy (Shift D). It is this copy that I now paste (Control E) in the center of my working page.
By the way, you will notice that I have named and saved my working page, too, and continually save as I work so that I won't accidentally lose it all. (Ask me how I know to do this!)
You notice that the working copy of the bricks is visible here. I click on it to make it active, Copy (Control C), and then Paste (Control E) next to the first brick image on my worksheet page.
At this point I am going back to View to click on Grid again, so that the page is clear, making it easier to work in lining up my images. I will return to View Grid when I want to place another section.
Notice here that you can still see the active Selection lines running around my second paste. I have decided here that I will click on Mirror to reverse the image.
Now I could just slide it over, butting it against the left side, ...
... but then it's too evident that it is a mirror image.
So, one thing I can do, I think, is simply slide it over so that it overlaps the brick with the 5 holes in it, thus extending the row of bricks. But oops, that doesn't work very well, either. Now there may be some other way that people do this, but at this point, I usually just start some judicious cutting and pasting along that center line so that it looks more like a continuous wall.
At this point I select a brick on the right, using the Lasso Tool from the Left Taskbar. (When I do this, I start with the larger bricks first.) Then I copy and paste it along the line wherever I think it might work.
So far, so good. You can also Flip it, too, so that it looks different.
Okay, besides copying and pasting whole bricks, here's how I remake a brick.
This one obviously needs some work. Quite often what I do here is select one side or the other, mirror the image, and paste it. In this case, since one side is larger than the other, I will work with the larger side.
Notice I have used the Lasso tool to make an irregular selection; I don't want it to have any straight edges.
Here it is pasted; now it needs to be Mirrored...
and slid over into place.
That's not bad; on a full wall, nobody will notice that one brick looks the same at both ends. However, if it bothers you, you can also Flip the image (while it is still Selected):
And there you have a new brick.
Another way to redo your brick is to simply do a bit of cutting and pasting inside it. Since the brick with the five holes in it is a bit obvious, we will just take the holes out of the one next to it.
Notice I've made an irregular selection here, and then I start pasting it to cover the holes:
I could just leave it like that, with the one hole, or I could paste again. Either way, it looks a lot less like its sister brick to the right. And by the way, notice that harlequin brick below it, for that one I would just copy the dark half, paste and mirror it.
Here I have done that, although not very well.
Notice the next brick; what we don't want is straight edges showing. Here I have made anothe irregular selection ...
And concealed that line.
And since that straightish line on the dark brick above is bothering me, I can select an irregular bit of the brick ...
and paste over it. Or I could select a bit of the opposite end, mirror it, and paste over it.
This is the two sections of blended wall after I have used the techniques described above. If there's still too much balance in it to suit you, too much mirroring, you can go back to copying and pasting individual whole or partial bricks randomly.
At this point, I would go back to View Grid, copy this section that I have just completed, and start pasting next to my first image again, etc.
I would probably move it a few inches to the left and then do more of the copying and pasting process to match it up.
This, on the other hand, is two pastings of the original image, side by side, with no mirroring. I have copied and pasted and remade individual bricks. Now these two different sections can be joined, and the process continued.The new section can also be flipped and pasted, too.
That wavy line along the bottom may have to be cut away completely when you start making more duplications; but then this is a very old wall, so a few waves might be expected, although more at the bottom of the wall than at the top, perhaps.
Remember that each time you make a larger section you can attach it to top, bottom, left and right, until you have filled up a page, either Normal or Landscape, depending on how tall or wide you want your walls. If you are wanting to do walls in smaller scales, you would do your reducing after all this work is done, not before.
One thing you will notice, too, as you work, is that the more you manipulate .jpeg files, the less definition you get. This makes a greater difference with some subjects than others and why it's good not to use your original. You can always go back and make another working copy, if you feel it's getting too blurred.
Okay, then, there you are ....
Maybe a professional graphics person wouldn't do it this way, but this is how I do it, and I've found that when I have used brick and stone made this way, it's hard to tell that all the walls were made from one small image.
And for what it's worth, these same techniques can be adapted to all kinds of other uses, as well.