Hi,
I just started a thief build and well, I have little problem to find some good quests to complete. My thief build is based just on pickpocketing, lockpicking, and stealing. Trying to avoid killing and combat at all. (maybe because I have only iron dagger).
I've joined a Thieves guild and completed thier main questline even the extra jobs. My question is: Do you know about some interesting thief jobs/quests in Skyrim?

Keeping doing extra jobs for the guild indefinitely? More trophies appear in the Cistern if you keep doing jobs. Other than that, just RP it and hit whatever feels right.

I did more than 125 extra jobs because I "won" that safe which is located next to guild master's desk and well, these jobs are not real quests once you reach this safe.