Some of the variants that use (or are rumored as likely to use) the base hull of the Armata include:
T-15 heavy IFV
2S35 Koalitsiya-SV self-propelled artillery system (this one comes with a separate posable barrel)
Armata TOS-2 thermobaric rocket artillery system
Armata MTU armored assault bridgelayer
A hypothetical Armata-based antiaircraft system, using the Pantsir turret
I'm going to work up some other versions -- mine-clearing vehicle, ARV -- and then I'll get some packs made up for sale.