They wanted me to match the style of the other artist's previous work so the background objects look different than the cartoon look of the animated sprites. I suggested we apply the cartoon look to everything for the sake of cohesion, but... apparently it would take too much time to redo all the things the previous artist had already completed.
And a quick little mockup thrown together in Photoshop to see how they might look in game:
Let's hope that someone with better organizational skills than myself will take care of the final level designs. :D