My only comment would be to consider the weather in your area. Be sure to have adequate heat in the winter and adequate cooling in the summer. Also is the "shed" protected from humidity? All of those factors can have a really wreck havoc on your photos, supplies, and scrapbooks. I've seen some absolutely amazing "scrapsheds" posted - just be cautious.
This was EXACTLY what I was going to say.
Depending on your climate, it could be a potential disaster.