Green stuff.
My fave thing to do is to add little pouches, such as Ragnar Blackmane has hanging from his right arm. To do this you simply get 2 tiny blobs of green stuff, stick them right next to each other (the top blob should be very very small). Then poke a hole in the top blob to make the top of the pouch, and taper the bottom blob by pushing the top inwards. Then simply use your exacto to make a few vertical lines on the pouch part. Look beside his hand in the pic.
http://www.newwavegames.com/gw/eventscoverage/gamesdayus01/lgimages/149.jpg (not my mini, just an example)