There's quite a list... let me fetch a part of it...
edit: so artists...
John Kim ([ JK ])
Alex Ahad (o_8 )
Bret Denslow (Mavdoc)
Andre Mina (Your-Fathers-Belt)
Tabitha Reed (pepper-tea)
Reggie Schreiber (Mobichan)
Justin Wong (fulltimefailure)
Jennifer Zee (jenzee)
Theresa Zysk (reapersun)
John Su (Bietol)
Josh Barnett (kirbyUFO)
Marissa Saradpon (crazy spork i am)
From the in game credits.
They outsourced too.
Can't say who did the 3D
FWIW, the artists Gaia hired to draw the artwork probably would expect... well, to be hired.
If you're not looking to hire, might I suggest checking the artists forums? You can likely find someone with the skillset you're looking for, and they may work for Gaia stuff.