I find it hard to have faith in a system that seems so suspect. I rejected religion as a child. Now, with loved ones who've gone to the other side I receive signs that these loved ones are still participating in my life. I still don't know what the other side is like exactly but I do have faith that there is something I can't conceive of, that I must wait to witness for myself.
Your picture of a sign that says This is the Sign You've Been Looking For? Why not figure out the person you feel most connected to that has left this realm and ask them to send you some sort of sign. Chances are it won't shake your world much at all. It might be a real comfort, like breathing deeply after holding your breath.
I think we are meant to live in this realm as fully as we can. It is an amazing gift, awe inspiring like kissing the top of a baby's head or hearing beautiful music (or whatever fills you with that certain kind of feeling.)
I wonder if you already have that which you seem to be seeking. Since I don't know you personally, do you think this might be true?
People on this side probably can't give you anything that looks like proof. It seems to me to be something that comes from a connection of love that is made tenuous because one person is left here, on this earth, where everything clouds our certainty. Love is certainly something that death cannot change. That seems to be some sort of key to the whole thing.