Bump mapping in SL?

Right, the big one, and I am sorry if I am going over well trodden ground, but a serach didn't turn up an answer.

Does SL support uploading your own bump maps, or are you stuck with the ones in game?

You are stuck with a very small selection of bump maps that LL provides. You can't import or create your own bump or displacement maps.

I thought as much. Thanks for the reply, though!

What's with the brightness/darkness maps... these seem to be generated. Sure, they're not infinitely useful, but better than nothing.

Closest I have come is to use a semi light patterned overlay texture and then to use brightness. It enhances the texture and makes it look embossed.

Yeah, you can sort of generate a bump map from the object's texture.
"Darkness" uses the texture's lowlights, "Brightness" uses highlights to generate the map.
Exactly how bright or dark they need to be for a good effect is kinda tricky... especially if the texture isn't greyscale.
I usually use pure black lines on a unicolor background and "Darkness" for things like door gaps or the front grill on cars. Looks especially cool on shiny surfaces.

Hmmm... but it uses the texture you assign to the object, I suppose?

Yes.