I took a look at the Blitz sourcecode. From Blitz's viewpoint, it has to at some point upload a pixmap to a texture before you can draw with it. That only has to happen once for multiple draws. I did not find anything in the source that looks like it's managing how many textures are in use or anything like that.
Like I said before, OpenGL itself manages the texture and moves them from video ram to main memory by itself as needed when there isn't enough space.
Like I said before, OpenGL itself manages the texture and moves them from video ram to main memory by itself as needed when there isn't enough space.