That's a really great custom you have there for a character I'm not too familiar with. I think I know who Jaster Mareel is from Bounty Hunter though (bare-armed Mandalorian BH guy? Hates Jango?).
The colors match up to what I recall of Mareel's outfit... They're unique. I like the Republic COmmando nod with the visor too, a nice little touch. I'm more into how you mixed up his duds though. Like the pack on his back, if it's the one I'm thinking, is a small reserve parachute for the Elite Force WW2 figures and has a knuckleknife on it perhaps? I can't see the pack too good but that's cool to me, and good use for that.
The aurabesh lettering is freaking awesome by the way. I've dl'd aurabesh for my computer so I have it incase I want to print it out and use it for something (anything) in the future. More people should make good use of the SW language like that as it's seen routinely in the films.
The gun looks cool and like a similar, but definitely unique weapon to Fett's sawed off blaster.
The Kama of course sets him off that much more...
If I had much of a suggestion, it's a removable helmet, but that's about it from me. That's really cool though man, good painting for certain too. Very nice man.