Designs by woebegoneart
No problem! It's one of those limitations that's not actually obvious from the seller's interface. You don't notice it until you start looking at other people's fabrics to buy. But Spoonflower's still in beta. I'm sure they'll get these kinks worked out eventually.
Unfortunately Spoonflower doesn't allow buyers to custom-size the print. The seller has to pick a size and that's what all buyers will get. If you want to offer different sizes, you have to actually set it up as a separate design (and order a new swatch). I do wish they'd let people size it themselves.