Rodrigo
Shohin
This weekend I went to a bonsai auction where they had some amazing and very old Junipers up for auction. As much as I'd love to have snagged one (or three), with my current space limitations and limited knowledge of Juniper I didn't think it'd be a smart decision right now. I settled instead for a shohin sized Ulmus Parvifolia that I couldn't pass up for $45. From the top of the soil line to tip of the tree is 7.5". I can already see it in a very shallow, long oval pot in the near future. 
Trunk:
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The roots have some work to be done on them apart from reducing the root ball for a shallow pot in the next couple of years.

It has some roots growing a little high on the trunk but I see a nice flare under them. Once I remove those and lower the soil line a bit it should look better.
Right now I don't like the roots being exposed the way they are and I'd like to address that but I remember @Adair M mentioned on another post that Up-potting into bonsai soil from nursery soil is a recipient for disaster. What would you suggest I do in this case while I wait to do a full repot?

Trunk:

The roots have some work to be done on them apart from reducing the root ball for a shallow pot in the next couple of years.

It has some roots growing a little high on the trunk but I see a nice flare under them. Once I remove those and lower the soil line a bit it should look better.
Right now I don't like the roots being exposed the way they are and I'd like to address that but I remember @Adair M mentioned on another post that Up-potting into bonsai soil from nursery soil is a recipient for disaster. What would you suggest I do in this case while I wait to do a full repot?