Here's my first attempt at illustrating my concept. I really don't know how to use the tools very well, so it was quite challenging just to get this far. The mouse in the back isn't finished yet, and I'm wondering if the style of the mouse in the front is too different from the style of the cat. I played around with adding a pattern in the floor, although I'll probably look around for something better for it, the wall, and the rug.
I decided to simplify the drawing from the original because I wanted something cleaner. The mice need work!
Here I'm imaging two bold mice sneaking up on and planning to scare a sleeping cat while timid mice watch from the mouse hole on the right. I may add some details such as cat toys for variety or put something in one of the mouse's hand, like a feather or bullhorn.