I've sent a few tips from the Family and Friends option since it is me giving them money for something I expect nothing in return for the exchange of the money. Since I've already paid for a service and the artist didn't request that I send them money that way they aren't at fault for anything and it is considered just giving a gift really. There's a very fine line, but the general consensus is along the lines that is as long as you aren't expecting a return, ability to get a refund, or using it to abuse the system then paypal doesn't care.
Also, be careful using the term "Tip" in any des