Here's some feature examples that could be used to enhance detail on maps. I'm very dissapointed to see only one map (The one with crystals) use features to much of an extent as of yet.
Why not have the units' tracks/treads/legs sink into soft sand or snow? Use a feature to cover the cround, also adding to the detail.
Have a Castle? Why not add some terrain differences.. Maybe a small pad covering the ground so your units don't leave dirty treadmarks on your base, and increase the texture resolution in the area?
Using 3D objects to cover ground can greatly increase texture resolution by using a tilable texture. Use features for Roads including stop lights, mailboxes, ect.
I'd be happy to release a common feature pack if I only knew how to convert my models. I can make the FBI's myself, but model conversion to TA/SPR has always eluded me.