Don't know about the value, but the theme is very interesting. Obviously it is a similar interpretation of "The Last Supper" made famous by Leonardo Di Vinci. The original painting has come under some controversy in resent years do to Dan Brown and the theory that the person seated to the right of Jesus is Mary Magdelene and not John. According to Gnostic Christian beliefs Jesus and Mary were a married couple.
Your version of "The Last Supper" appears to me to take a more provocative move towards the Jesus & Mary theory. Notice the person associated with being John in the original Last Supper is actually laying thier head on Jesus' shoulder in this version. The person also seems to have a more distict feminine hairstyle. Jesus has his arm on his/her shoulder showing a very intimate relationship with this one person compared to the rest of the disciples.
Interesting in this interpretation that Judas is clearly not part of the emotional action, and is holding his 30 pieces of silver in a bag in plan view.
With all that said, It still has the feel of a cheap tourist piece. Granted, it my have cost some American tourist $150-$250, but it just doesn't look like something that valuable on the re-sale market. I am not an art dealer or expert by any means, so my opinion is just an uneducated one.