Thank you Jacob, but Bitcoin doesn't fulfil one of our requirements really well: it's value isn't as clear to people, as other currencies are. We have Bitcoin support in our backlog, but to start, we would prefer offering official currencies to our users.
Alberto, I will have to talk to the developer who told me about Skrill not being a possibility. Thank you for letting me know, I'll have a look at it myself together with Balanced and Bill.com as suggested by Alan and Ray.
Another service I stumbled upon is Tipalti. Any thoughts on them?