Hi Steve,

do not waste any efforts converting bitmap textures to JPG, to solve this internal memory issue. These files would immediately get uncompressed again by Bryce, when loaded/used in your scene, which is logical.

JPG files will only save diskspace, as external files. Besides, consider, that a JPG compression will always reduce the image quality and might cause noticeable image/detail artefacts. If you intend postwork, always use a lossless image format (e.g. TIF, BMP,...). 

Hubert

"All that we see or fear, is but a Sphere inside a Sphere."     (E. A. Pryce -- Tuesday afternoon, 1845)