I have a question on material types:
There are available materials such as "Doodad", SpecialFX" and "Building". They seem to look exactly the same as the Standard material does.
Is it better to use those materials for (respectively) doodads, particles (?) and buildings instead of the standard one?
Using "Doodad," "Building," or "SpecialFX" should be equivalent to using "Standard," though it's preferable to use "Standard" these days. At one time, those material types existed separately, but we folded them all together. They continue to exist as stubs to support some very old models we have at Blizzard, but they shouldn't be necessary for any new model.
And thanks for the kind impressions on the Art Tools, Leru! The developers responsible for creating and maintaining them frequent these forums and really appreciate the time and effort you and the other testers are investing in putting them through their paces.