UFC Hottie Brittney Palmer -- I'll Paint You A Picture ... For $6,000 a Pop

If you thought Brittney Palmer's ass was a work of art ... wait'll you see what she does with a paint brush.

TMZ Sports has leaned the UFC ring girl has built up a pretty successful side business as a painter -- and the going rate on her stuff is around $6,000 per painting.

We spoke to Palmer, who tells us she's always loved art, but didn't get serious about it until 4 years ago when she enrolled in art school ... and it blew up from there.

"I posted what I thought were these sh**ty, sh**ty, paintings [on Twitter] -- but people contacted me and asked to buy them," Palmer says.

Brittney says she's been hired to paint for all sorts of celebs, including computer guru Michael Dell and UFC fighter "Mighty Mouse" Johnson ... saying, "I usually get $3,000-6,000 for each painting, depending on the details."

But there's one person who doesn't have to pay ... Brittney's BOSS ... UFC honcho Dana White.

"I did a Muhammad Ali painting for Dana," Palmer said ... "It's not on the wall, but he still has it."