I find the look of dead standing trees in a pond quite aesthetically pleasing. A pond needs structure, and leaving trees standing can do that. My dad's 2 acre, 10 ft deep Iowa pond still has dead oaks standing that were flooded in 1978. The dead trees are also more fun to fish around IMHO.

I think the major concern with leaving trees is that you are not able to compact the dirt where the tree trunk is which could lead to a leak. A pond with 100 gal/min flow should be able to withstand a few leaks.

The other concern is tress falling, but the likelihood of being under one when it happens is pretty small. Just don't build something near where one of the dead trees will fall.

Every person should have an interest in life - I think I'll go fishing. ~ Thoreau