Is it too forward of me to suggest that you not get a tattoo?
I seriously mean no disrespect, but a tattoo is just one of those things that you can't get rid of, ever. If ever a day comes in your life where you feel you are ready to move on, the tattoo will always be there no matter what you feel at the time.
As far as suggestions go, I think the inside of your arm is a great place, seeing as how it's for you to remember him by, not for everyone else to see how much you want to remember him. Try to go subtle. I like the sparrow idea. It seems pretty cool.
Leave out dates and initials. It makes the tattoo too obvious. I think the beauty lies in only you knowing what it truly means.
edit: posted this before i knew you already had tattoos. I guess that negates my first three lines
