Which memory does LoadImage/LoadAnimImage use?

I am setting a 3d mode but use 2d functions as well. i want to make a side scroller with some 3d elements in the back. Sprites look nice and sharp when drawn with 2d functions, if I texture a 3d sprite with the sprite, it looks blurry because I can not get the pixel perfect translation (i.e. 32x32 sprite occupies more or less 32x32 pixels as a 3d object, but not exactly).

I was just wondering in terms of speed. Thank you guys.