Tactical semi choice

[Blackstuff]

Is there much aftermarket tarting up stuff available for the Sig?

No, and you can't even chop the barrel because of the folding stock Unless you have a real hard-on for the look of the rifle personally I wouldn't bother

[Gazza]

No hard on's, those days are gone
By tarting I mean improvements like triggers, furniture etc
I must admit I have failed to track down any improving tarty bits for the sig.

[Blackstuff]

While i'm sure a proper gunsmith could improve the trigger, at a cost, AFAIK there are no simple drop-in units like their are for AR variants. The only furniture options are the plain handguard and the railed one. If you're wanting a gun to tart up as suggested a 10/22 has a miriade of options, or a 15-22, but as you already have a CMMG AR thats probably less attractive.