It breaks with uppercase file extensions.

[MatLegat]

I've been using your tool for donloading boxart for various ROM games that I have, and I've fount an issue with your tool:
When a file extension is in uppercase it recognises that it is a rom (tries to download a boxart for it) but then it can't check the type of it.
This issues happens with various rom types (.GG, .SMS, .GEN, etc...) and renaming the files for them to have a lowercase extension (.sms, .gen, ...) gets rid of this error (at least on my tests).

Output extracted from the tool with an example of this error:

01:21:28 - Searching art for Bram Stoker's Dracula.SMS.. 
01:21:28 - Something bad happened: Unknown ROM type.

Anyway, thanks for this much useful tool for TwilightMenu users :)

[KirovAir]

I'll have this fixed in the next version. :)