I like the graphics on the t-shirt. Very attractive!
If I may make one suggestion, it would be to add the fact that it literally is an acronym for "Hold On for Dear Life"...and that's an important part of this thing called Bitcoin. Early adopters were getting in to support an idea, not as an "investment". People that are getting in now have to be ready for the wild swings we endure. Bitcoin will lose 30% of its value in a week, the news will start talking about "crash, crash, crash" and then it'll pop back up 50%!
You can't predict these swings and you can't mitigate your exposure either...you just gotta hold on for dear life!
I debated that, and it appears there is a split consensus on whether or not HODL is an acronym or not. Looking at it's origins
https://bitcointalk.org/index.php?topic=375643.0 you can see that it did not start off as an acronym but rather a drunken misspelling of HOLD. I decided to keep it true to it's origins in my definition to avoid the controversy of the acronym.
