I've seen glaux.h used in a lot of OpenGL demos to do stuff like loading in BMP files as textures. This makes use of the AUX_RGBImageRec structure and the auxDIBImageLoad() function. I'm looking for a replacement for that functionality -- is there no mac equivalent header that does the same stuff?

There is no mac header that does that.

You can copy the code from QTValuePak (http://203.79.121.211/~keith/Code) to load any image QuickTime can read as a texture. It's pretty easy.