I know... there are plenty of shelf brackets on Thingiverse, but I couldn't find anything ornate, so I made my own. This is designed to fit a 1x4 piece of wood. Odd size for a shelf, I know, but this is designed specifically to hold my girlfriend's MANY Pez dispensers. There is about a 4-5mm gap to allow for wood that isn't perfectly 3.5" wide. After I printed this and took the photo, I added a small hole on the underside of the lip to accept a screw to hold the shelf in place. The .stl has this hole.
If you want to print this to fit a 1x6, scale it up 145%. I haven't tried this, but the math works, so it should work.