Margaret Cho -- There Will Be Blood ON MY WALL!

Margaret Cho got a painting made out of her own blood ... and it actually looks pretty damn cool.

BACKSTORY: NYC artist Vincent Castiglia made a name for himself by painting with blood, so back in April she commissioned him to take 72 milliliters of her red stuff for a portrait.

Cho wanted Castiglia to use her menstrual blood ... but he pulled the plug because her production level was woefully deficient.

The piece took 6 months to complete. It would normally cost around $20K -- but since he and Margaret are friends, Castiglia hooked the comedian up with a solid, undisclosed discount.