A few months ago I took a stab at creating a simple, fake video game interface after an potential freelance client inquired about my abilities. I took an evening to quickly design it and then another evening to animate this brief video in order to show how it might work. I love illustrating the most but this is often the sort of stuff that helps to get the bills paid for me.
If you're struggling with making a living with your illustrative work alone then I always encourage you to branch out and try other areas of development as well. You can learn a lot and it can help make you a more valuable asset to others! Hope you like it!