1) the HYYH logo. It is short and meaningful. As people have mentioned here, have the tattoo artist draw it out for you first before inking you, to make sure he/she is writing it correctly.
2) I love the Spring Day verse. It will be kinda long, so it’ll probably will have to go on areas like your forearm, shoulders, down your back, etc.
3) The LY Series hearts. Every BTS stan/fan would instantly know what it is. Make sure the drawing is clean and crisps, otherwise it will just looks messy.
4) Jimin’s drawing. Just because it’s pretty and I’m partial to Jimin.
Good luck on your choice. And make sure to post here aftee you get it done.