For me it would have to be a tie between this one:
...which was difficult because I went crazy with background details. Most of these details are lost when the image is reduced to fit this forum, but I actually drew the corduroy on the couch and cushions, the pile on the carpet, and the wood grain on the table and hardwood floor. I don't even know why I did it, I just couldn't help myself. Like I said, this detail was all lost on the upload anyway, but believe me, the original 7200 pixel wide image is impressive.
...And this one, which is also the most recent that I've done. Nine fully detailed human characters, a golden eagle character, and the inside of the palace's throne room, complete with hardwood floors.
The skin and hair colours are natural on these characters. And I couldn't draw a throne room without drawing a throne, so even though it got covered by the people in the foreground I drew it anyway. It is inspired by Napoleon's throne. Here is the background layer:
