Plan created by Trainboard member @gary60s . The download PDF contains the full plans, images and templates.
Here is a storage rental garage in the modern "Rix" style. I've seen many of these in a variety of sizes. The individual storage spaces in this one measure 9' by 12' Overall footprint is 1 7/8 x 2 7/8, and you can make as many as you need for your available space. If you don’t like the colors, you can paint as desired. There are parts templates to print so you can save measuring steps.
Choice of materials is up to you. It can be done in wood but sketches are based on styrene thicknesses. If you use another material adjust dimensions accordingly. Paint parts before assembly, except where the edges glue to other parts.
The building directions and materials are in the sketches, and to make your build easier you can enlarge them to full size and print them out. Read directions in assembly sketches before cutting out parts as you may want to change some sizes or cut fewer, or additional, openings. Included sketches are: Overview sketches, Assembly sketches, Parts templates, and PDF's.
To print the part templates actual size, use the PDF's. Select best printer quality, set PDF zoom to 100%, and page scaling to "none" or actual size. Check your printed page to see that 3" lines are exactly 3" long. Once you have template printed, you can cut with scissors (leave a 1/8" border) and arrange on your material for maximum sheet usage. Part templates for siding are a mirror image, when needed, so that you can cut walls with siding side down (easier to cut). Be sure siding grooves are oriented correctly. Use rubber cement or Krylon Easy Tack Repositionable Adhesive to glue paper templates to your material and then just cut on lines. No measuring ! Paper comes off easily.
Cut out parts carefully using a SERB and straight edge. It is important to follow assembly sketches IN SEQUENCE or some parts may not fit.