What could Tess be short for? Besides Therese...

I think [name]Esther[/name] could work! But here are a few names for you to look at;

[name]Tressa[/name]
[name]Thessaly[/name]
Tassia
[name]Tasmine[/name]
Contessa
[name]Theodosia[/name]
[name]Estella[/name]/e
Tessalyn