Levi Johnston -- TRIPPIN' OUT in Family Christmas Photo

Bristol Palin's DNA will always have a special place in Levi Johnston's Christmas family photo ... at least in the form of the ex-couple's son Tripp, who made a red-sweater'd cameo in this year's snapshot.

The photo was taken last week for the Johnston family Christmas card inside Levi's Wasilla, Alaska home -- and it looks like everyone agreed to wear some kind of plaid ... or argyle ... except for Levi's new wife Sunny Oglesby.

As we first reported, Levi is strongly considering a move to get full custody of Tripp -- believing Bristol is a bad parent ... letting Tripp run amok at home ... talking back, cursing, and disrespecting his elders.