You might be kind of hard pressed to find a market for people willing to give you Bitcoin just to send memes to someone, but I guess it is possible to make money off of it.

The biggest thing I see here is that you're charging $30 for a postcard. Charge something like $5 or $10 with mail included and you might have some people interested in it.

While it's always better to make more money when possible, $30 for a postcard (resulting in $28 of profit) is going to be next to impossible to justify.