To store drawings we bought a plan chest from eBay, from a retired architect - it will also make a great table for preparing canvases. I've also built bookshelves from spare roof boards and put up the odd coathook, but apart from some tidying of the outside of the cabin (we want to add a simple deck around it) we're pretty much finished:
The new studio is very light due to the skylights we added, so at present there's little need for artificial light - although we plan to add some solar powered ones at some point. It currently has no source of heat: we have a Calor gas stove which could be used (although condensation may be a problem) or we could add a woodburner, but since it's very well insulated it should be usable without heating for most of the year, given enough jumpers! I have some plans to add a greenhouse on one end, which may open up options for passive solar heating.
It's been around a year now since I started the project - Alex is very happy with her new workspace and looking forward to creating art there. Hope you've enjoyed following the process!