If you have never done it, I suggest you pick a nice sharp ray-traced render and compress it in various JPEG compressions, then reopen the images and also compare file sizes. JPEG does amazingly well, it mostly suffers in hard edges, there are little artifaces around them- but most texture maps aren't all that critical on edges, anyway. I often use 1500 x 1500 texture maps, that would over 6 Mb raw filesize, probaly about 2-3 Mb as a Zipped tif, who is going to set through downloading that on a modem? A high quality JPEG will be only about 300K. One thing to remember though, don't use JPEG internally, just for sharinging files. If you keep reopening, modifing and resaving the file in JPEG the degradation keeps adding up. Incidently, I've never seen any modern program on the PC or Mac that had trouble with TIF, there is a option for Mac or PC byte ordere in Photoshop (has to do with LSB first), but there is also a flag in the file for the byte order, so it shouldn't make any difference what you pick.