Good news, anandparikh!
Security Response have confirmed that definitions available now via LiveUpdate (Sequence number 154205 - "5/25/2014 rev. 20") will detect and remediate those files as Trojan.Gen.2 (for Thumbs.db) and Trojan.Gen (for RM (4GB).lnk).
Please download these latest definitions and run a scan of the USB thumb drive. Check the logs, afterward, to ensure that all files have been detected and a successful action carried out against them.
Update this thread, after, with your results! &: )
Mick