Congratulations on starting to sell your stuff!
I wouldn’t worry too much about international customs, though. You can just set a policy: purchasers are responsible for any customs and duties assessed, you declare all items at the purchase price, etc. Then it’s up to people to decide whether or not it’s worth the potential costs/hassle. Of course, there’s a bit of paperwork for you to fill out when you’re mailing items out of the country; however, once you’ve found out the requirements from the post office, it’s not excessively complicated.
From the US to Canada, items $30 or so don’t hit the “worth the hassle of doing the paperwork” for the customs people (at least that’s been my experience). Even then, original artwork is exempt from customs and duties (as are pretty well all made in the US items — one of the nice things about Free Trade), at most people here in Canada would pay provincial and federal sales tax, plus a $5 service charge from Canada Post for processing the customs clearance. It’s only if items were shipped via UPS Ground that customs clearance across the border gets crazy expensive.
In any event, congratulations once again. And good luck with the sales!