Oh - bump it up to at least 60 in bump (if not 100!) - not gonna notice much under 20. Didn't realize you were setting it that low. Then put a light shining across it's surface (angled so it's to the side of your material casting shadows across the surface) and do a test render. Bump maps don't actually chage REAL height - just the way the surface reacts to light so it APPEARS to have lumps and bumps - saves you from having to make a HUGE polygon count in the model's surface geometry. So, also, you're not going to see anything until you hit "render". To save render times, though, just open a new document, make a cube and apply the texture, and make a side-light. Don't do it in a complicated scene until you like how it reacts.