My experience with bonsai is limited but I believe that I do have a good eye for aesthetics. I have looked at many bonsai in the past 2 years and studied the tree to pot relationship quite closely.
Here is my opinion on a pot choice for this tree:
While I absolutely love the green pot it is in, I think it is far too fancy for the rugged look of this elm. I envision something more dainty in this pot.
What I imagine for this tree is a very dark chocolatey brown unglazed rectangle with smooth corners.
I did a virtual repot that you can view it in my gallery. (I didn't have anywhere else to upload to other than village photos, but they only allow small compressed images)
Hope you like it. It was my first ever attempt at a virtual.
Joe Mc