You might want to check out one of the best bonsai threads on the internet by Arthur Joura of the North Carolina Arboretum. Adding to Judy's comment, I have one I did myself, which I will just keep private LOL.
I've seen some very very good examples of this done with spruce forests by some Japanese masters. Although never with a fallen tree. That would seem difficult.
Goshin has a dead trunk or two doesn't it? Can't tell in the pics of those long dead trunks have any live veins or not... none are fallen obviously, just saying that is a rather famous example..
American Larch Group Setting, 3 yrs old and a WIP, will be adding 6 new Larch this Spring, Foliage just starting presently, one downed tree trunk shown & I may add another...