Random interior paintings have been a favorite of mine for a while. They are usually very hard and full of random assemblages of day to day stuff in anyone’s home.
I find them a good challenge and training because you have to focus on exactly what your seeing rather than any internal idea of what it may look like. This is much different than painting a still life of an orange or a flower. I tend to have a lot of internal ideas of what these things should look like and that in turn effects how I paint.