Blitz3D supports 8 textures with 2 UV sets, I believe.
Yes, I know it supports 8, but it automatically renders multiple passes if the graphics card can't do 8 in one pass. What I don't know is how many DX7 allows in one pass. Just because the videocard can do 8 or 16, doesn't necessarily mean that DX7 could do it. DX7 is so old now that it's hard to find accurate information on what it could do unless you've got books from that period.