If I load a texture which I want to tile across a surface, that's pretty easy to do:

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

And then just specify texture coordinates outside of the range 0 to 1 when I'm drawing stuff. However, as far as I can tell, this will only work for textures I've loaded from a single file (like an image of brickwork which I know tiles properly). If I want to incorporate that brickwork into a sprite sheet, with a bunch of other textures as well, I'm not sure how to wrap. Say if my sprite sheet is divided into quarters, and the brickwork is the top left corner, it's bounding texture coordinates are (0,0) and (0.25, 0.25). If I specify texture coordinates bigger than that, GL won't know that I want it to wrap and will start rendering bits of the other 3 sprites in my brickwork. Is there any way around this, or is the solution just to load all wrapping textures indvidually, and save the sprite sheets for things which don't wrap?

I'm not really sure what you mean. Do you mean that the only way to wrap a texture which is part of a sprite sheet is to draw it as multiple quads? Or have I completely misunderstood?

I'm vaguely wondering if there could be a solution which involves loading a spritesheet as one file, but then splitting that file up into multiple textures in memory, so the end result is pretty much what you'd get if you'd loaded all the textures seperately. It would save a bit of time doing the actual loading, but I guess that way you still pay the overhead of switching between different textures when you're rendering a bunch of sprites :-/

I'm not using shaders, no. I might look into them, but for now I'm just trying to keep things as simple as possible. I've not heard of a "tile atlas" before, so that could be where I'm misunderstanding you.

I've not had a chance to try out what I think you're suggesting yet, but it kinda sounds like you're saying that if I have a sprite sheet with 4 textures, laid out like this:

AB
CD

Then to draw a quad with A tiled 4 times, ie:

AA
AA

I'd need to do something like this (clockwise, from top left)

glBegin(GL_QUADS);	glTexCoord2f(0, 0);	glVertex3f(-1, 1, 0);	glTexCoord2f(1.5, 0);	glVertex3f(1, 1, 0);	glTexCoord2f(1.5, 1.5);	glVertex3f(1, -1, 0);	glTexCoord2f(0, 1.5);	glVertex3f(-1, -1, 0);glEnd();

Is this right? As I say, I haven't tested it, but in my head this would give me a quad textured like this:

ABA
CDC
ABA