Search for craft rooms on houzz. A 22 foot by 22 foot addition is not small or compact. Include a bathroom and perhaps a big sink with cleanout on an exterior wall for dye work. Consider closed door cabinets under a row of windows. Consider north/south exposure preference for the natural light.

If there will be a full size hand loom, try the forums devoted to weaving for practical ideas.

I see this is an old post, but, I am currently customizing my studio and put in 2 closets. The studio is 16 x 20. The closets store all my show stuff. On one small wall, I'm adding a built-in cubby to store other items. I'll post some photos for you!

This photo is with a very large closet to store tent and a rolling art storage cabinet to hold pro panels and/or canvas art. There is another door on the left which is standard. If I want to make it a tiny home later, this closet can become a room for a nightstand and night table.

It's a little hard to see here, but there is a closet to the left of the window. There is a large piece of sheetrock leaning on it. That will store stacked bins on a platform that rolls.

This photo gives a more realistic view of the scale of the room. Those chairs are quite big. Storage that is completely out of sight iss the most important factor for this space.

This is the storage bin. I put it on wheels. It holds an entire 10 x 10 pro panel display.

This is the type storage cube I plan to use and add the decorative storage boxes that slide in and out. The above "Lachlan" is from Lowes.

This is the storage bin. I'm using something similar, but more decorative. They have some nautical covered ones and leather ones as well.

I will eventually add water, but I may have to add on to the outdoor deck and enclose that. A sink is a must! I used to dye and also recommend a stainless steel counter top or kitchen-type sink. A washing machine would also be a great addition.

This is the studio model I first created when I was going to add a 77 inch sink and counter on the inside. I wanted more space and the extra cabinet. You can see the large box closet with the white top. There is a loft over that and the cubbys are on the back right wall. I also added space for hanging a kayak which i have since been rethinking now that I've sheetrocked the walls.

Penland School has an awesome fiber studio. One for weaving and another for dyeing. I don't have any photos, but there are probably some on their site. If not, also check the Surface Design Association or with their members. A search for She sheds might turn up some inspiration for design. Did you get it finished? Hope this helps!