MAMEWorld Forums - EmuChat - Re: Pretty much finished Cab. Now what...

You could spend some time on the software side of things, playing with front-end alternatives, adding other emulators for systems you might be interested in, etc.
There are several console games, particularly fighters (if you like those) that lend themselves well to MAME cabs:

-PS1 (recommend ePSXe): Riden Project, Mortal Kombat Triloy, early Tekken titles
-Dreamcast (recommend NullDC): Soul Calibur (better than arcade), Mortal Kombat Gold (better version of MK4)
-Gamecube (Dolphin): Soul Calibur II, Mortal Kombat Deadly Alliance & Deception
-PSII (PCSX2): Soul Calibur III, Contra: Shattered Soldier, later Tekken titles, Virtua Fighter IV Evolution, Dead or Alive 2 Hardcore
-Wii (Dolphin): Mortal Kombat Armageddon, Tatsunoko vs Capcom
-PC: Bionic Command Rearmed, Street Fighter IV (one of my favorites my cab right now), Super Street Fighter IV Arcade Edition (releases in July), Street Fighter X Tekken (coming in 2012)

There is also the plethora of Sega Naomi and Sammy Atomiswave games that MAME runs very slowly but run great in Makaron (for Naomi) and Demul (for Atomiswave and Naomi vertical games).

That's just to get you started but there are many other games that could be playable in a cab and you might like.

Good luck!