I like how it captures the WW2 grainy film feel, but it just seems boring without color.
And don't tell yourself, "Don't use brushes no matter what". If you can use them in creative ways that benefit the final product, then go ahead. Just don't use them as your primary method of creating backgrounds. If you want to become more creative with your brushes, take a white canvas and put a single stamp from a brush set on it. Think of what it looks like, and build your sig around it. You may not get the most desirable results, but it can help expand your creativity, which will help you come up with better results later on.