This will be a quick and easy idea. When I wanted more shelving for my room, especially to put up little nic-nacs, I made use of an item I already had without spending a dime.
All I did was take a drawer from my old broken dresser (it doesn’t have to be a drawer but you can use something similar to this) and nail it to the wall to create more room. Put the bottom of the drawer closest to your wall and the handle at the top. An easy way to make it look nicer is to put cloth inside the drawer to make it stand out. You could also paint it however you want. It’s simple and can hold pictures and whatever else you want to use it for.