Anything you do to "promote" yourself and your girlfriend comes from a position of weakness; you're either doing it because you want to show her off (which means you value her very highly and put her on a pedestal) or you feel like you want to satisfy her by doing "nice" things for her (which means you're a bit needy).
This is a false dilemma. It assumes those are the only two possible reasons why you would post pictures of your GF. Although those are indeed possibilities, here are some alternative reasons:
- You value her and want to show her off
but you also value yourself. You see both of you as valuable and want to show the world. It's not necessarily putting her on a pedestal.
- You want to let your friends/family know how you're doing. She's a part of your life. Therefore, you'll have pictures of her ( e.g. I've had a lot of family members ask me to post more on FB because they have no idea what's going on in my life).
- You want to satisfy her because you genuinely love her. Not out of fear of losing her. Just because you know she would appreciate it. It's no a no-strings-attached gift to her.
- You think the pictures you have of you & her are cool. Independent of the fact that you're in a relationship.
- Similar to the previous point, you went on a cool trip or vacation with her. And you want to post your experiences there. Independent of her and your relationship with her. It just so happens that she's in some of those pics.
...and the list goes on and on.
Generally speaking, I understand your point. If you're CONSTANTLY posting pictures of you & your Gf and nothing else, it can come off as a little weird. Almost looks like you have nothing else in your life. But if you have photo of you+your gf, but also others of just yourself or of you+friends or other activities etc, it seems ok to me.
But ultimately, Facebook isn't all that important anyways. Unless you do something very unusual and outrageous which attracts lots of attention, the shit you post on there probably won't matter.