I don't know if it is too much work, but you could draw traditional sketches, sign them with cute little messages and then mail them to people.
My only concern is the price of international mailing lol

I dunno... I've always supported my favourite artists without wanting anything in return and I like it that way. Of course when artist will give me something in return I will rejoice! But it's like buying a CD from the band or going to their gigs/concerts - you're buying it and therefore you support them to do more music. Supporting artists should be like giving them time and media to create more - not taking the time because you think that they're obliged to give you something because you helped them.