My wife was sick of the storage bins of filament in the office. So a few years ago I create a 3d printable wall system to store my filament spools and miscellaneous 3d printing periphery. I wanted a system I could modularly add to as needed, easily 3d print, and was very strong. I needed to use easily obtainable rails, so I used 1x2 select pine boards (i.e. 0.75" x 1.5" dimension). All part dimensions of the system are based on that nominal lumber, because in the US they are cheap but can look good if you want to sand/stain it.

Please note assembly requires screws. The type used is not critical so long and the diameter and length is appropriate. I tend to use pan head sheet metal screws where the screw head bears onto the plastic. This is to avoid the wedging/splitting across layer lines which can happen from standard bevel headed wood screws. If you intend to hang a lot of weight make sure the 45 brackets get screwed into studs wherever possible, or use high quality hollow wall anchors to distribute the loads.  

Some of the screw locations can be more difficult to get to during assembly since I worked to keep most of the screws hidden if possible. I found it useful to predrill the screw holes into the wooden rails prior to assembly to ensure threading the screws was easy using simple hand screw drivers.

If you want to modify it to better suit your needs all files are in STL, Step, and the native Onshape file is linked below. I hope you find it useful, or use it as inspiration to develop your own solutions.

Onshape Link: https://cad.onshape.com/documents/5c7fcbed4b49e1bf0c96ab71/w/42bde484466584e5b26cc861/e/d0490f2013f018618229b5d9?renderMode=0&uiState=679fd9f08674f77ee824265d