After a few days of worry and stress, I finally have a resolution to the situation where my Okami fanart:
was being used in a banner/tickets for an Okami convention in Barcelona. On the one hand I'm flattered, on the other I was horrified to know my art might have been being used for someone to make money for themselves. Particularly without my consent or any credit or recognition.
I tried for several days to talk to the convention creator and never got a response. So I did all I could do and reported it as a copyright infringement to Facebook. After a short correspondence with facebook services, I figured they would simply remove the banner and be done.
I was very pleased and surprised this morning when I got an e-mail from the convention creator (finally) with an apology and request to use the image until the event was over with credit given. Facebook had taken down the image. Though the people had banned me from the event so I couldn't see it or attend it anymore! HA!
Since I'm not a spiteful person and they had already put a lot of work in on the event, and I would never want to hamper the fun of others at a anime convention, I agreed to allow them to use my image with credit given. I even gave them an original copy so they might be able to update their banner with a nicer version of the picture if they so desired.
I don't make art for money, I do it for fun and as a nice stress-reliever. I'm very pleased to tell you guys that even if someone has stolen your stuff there are still people out there that will help. Even big companies like Facebook, of all things, saw the wrong in their actions, and forced a resolution to the problem.
Thank you everyone with your support throughout this upsetting situation! You all helped me a lot with your kind words and helpful attitudes!