Hmm...Oh...OH. I can see a problem here.
For this image, assume every pixel represents 8 pixels. Thus, a 2048px OpenGL texture would be 256px here. Using the same scale, a 24px, 32px or 48px tile sheet would be 48px, 64px or 96px respectively.
Assuming you can break up a sheet into smaller parts, you can snugly fit 28, 16 or a measly 7 sheets onto a single OpenGL texture. These numbers would quadruple if you're working with 4096px OpenGL textures, with a hard limit of 115, 64 or 28 sheets.
So...depending on your resolution and number of tile sheets, there does seem to be a reachable limit here. GemSet currently uses 12 sheets, so the 48px version would be unusable for people with older GPUs. Even moreso once I add in the building overrides, huge workshops and mod support. Not to mention, I'm not even thinking about the creature graphics here.
I'll try my best and see if I can trim the current tileset down to about 6 sheets. If that's not possible, I'll look into making a Lite version so 48px will work for older computers.