ElectroCelt merchandise (t-shirts, posters, prints, cards, mobile phone cases, laptop/iPad skins, etc) are exclusively designed by AlyZen Moonshadow, and are generally available for purchase on her sites here:

http://www.society6.com/alyzenmoonshadow

http://www.redbubble.com/people/alyzen/shop

http://www.zazzle.com/alyzenmoonshadow

http://fineartamerica.com/profiles/alyzen-moonshadow.html

http://alyzenmoonshadow.deviantart.com/gallery/

Do check back often, as AlyZen will be adding more images all the time.