I always encourage my kiddos to sketch lightly in pencil first, and then use a sharpie to outline the good lines they want to keep, and erase old pencil lines. It adds a few minutes to the finished product but I think it is worth the time. We used colored pencils to color and shade.
While students finished coloring and some added a background, I played a few end of the year videos from my youtube 'end of the year' playlist. I also really like the animation Planets on Vimeo, but I always stop it before the 12th planet as the last song isn't age appropriate, the rest of the video is pretty engaging.