Is my boyfriend gay or bisexual?

I promise I'm not trying to be offensive. I'm 20 and never had a real boyfriend before. I was never allowed to. My mom was extremely religious. Extremely strict. I went to an all girls Catholic school and haven't really gotten to ever explore life and now that I'm away from my crazy mom. I have a boyfriend. Why I'm wondering if he's gay or bisexual is because he has a picture with one of his guy best friends. They went a few years back to this music thing. He mainly want to see my chemical romance but it had that type of music. I guess goth music? I do not know the right term. Anyway I do understand my boyfriend is kind of a short king. He's still taller than me. I'm only 5'1. He's 5'5 in a half. The picture is he's on his best friend's shoulders who is 6'3. He he couldn't see so his best friend put him on his shoulders. Is that normal for male friendships? They were 18 when this happened. I guess I really don't understand male friendships and if that's normal or if he's bisexual or gay.