Yep!!!
I don't have a single engine (yet) that has not been modified in some way. From fixed pilots, Kadee couplers, crew added, LEDs, electronic packages (ERR Cruise Commander, PS2 installed), repaint, all the way to taking my Dremel and cutting away a Bellpaire boiler to make a RailKing 2-8-0 into something that looks more like a Seaboard Air Line engine.
When my 3rd Rail E7 gets in that may be the first engine not to get modified.
Atlas GP9 with PS2 installed:
MTH RailKing NW2 with fixed pilots and Kadees:
Williams E7 with the works:
RailKing Imperial 0-6-0 repainted for Seaboard:
RailKing 2-8-0 re-worked to look like a Seaboard engine. I have since blackened the siderods. The Bellpaire boiler was removed, the walkways changed, the domes moved, and the headlight moved. Engine originally came out of a RTR set I think (won off EBay):
The only engine I didn't show is a RailKing RS3 (just haven't taken a photo yet) that has the pilots fixed and Kadee couplers added (all engines have fixed pilots and Kadees)