Some great suggestions, he does look just like a Sylvester, although with our other cats we seem to shorten there names e.g Mitzi we always call Mit or Mits so Sylvester would probably end up being Sylv

a bit girly maybe?
I kind of like Squirt, its funny, better than what I have been greeting him with 'hello smelly'!
Minstrel is good, not sure though, am I being hard to please yet lol!
Boris would suit him well, but my mum had a cat called Boris.
Barry lol can't help but think of Barry who used to be in eastenders!
Mac could work to, and hes quite a big cat so he could be our.... big mac!

My b/f likes Shadow and Bilbo.
Ok I think were gonna test some of these names out with him next time hes over see what he thinks!