You can fit 16 256x256 textures into a single 1024x1024 texture. You can fit 4 512x512 textures into a single 1024x1024 texture. You can go bigger than 1024 on a side, but make sure you use mipmaps otherwise, if you video card doesn't support a texture size of 4096 on a side, you'll get errors.
"You level up the fastest and easiest if you do things at your own level and no higher or lower" - useful tip
My 2D game - release on Jun 13th; My tutorials
