Absolutely, we're currently doing mugs for TWiT (www.teespring.com/twitmugs) and our plan is to branch out to other items - we just want to make sure we can deliver an amazing experience in each product category before we expand to the next.
If you shoot me an email at walker (at) teespring (dot) com I'd be happy to work with you to setup a poster campaign.
Will definitely be using your platform in the future , it's exactly what i was looking for.
Any plans on crowd funding posters in the future?