You don't want her to dress like "everybody else" but you want her to dress just like the chick in the picture? Okay, that way she can follow some other crowd, except it won't be the one she wants to be in. You want her to change her style for the sole purpose of pleasing you even though it's not what she likes--that's pretty selfish. You either need to accept her the way she is and drop the fashion issue, or find another girl.
Um...that is pretty ugly in my opinion. I could understand if she had like 0 style and you wanted to upgrade her to normal or like everyone else. That hottopic stuff is very specific to a certain type of person. Meaning if she doesn't already dress like that its probably because she doesn't like it.
If the gothic style is so much of an issue for you, why didn't you start dating a gothic girl from the beginning? It would have made a lot more sense and you wouldn't even have this issue. I know you said you love your girlfriend but you didn't fall in love with her overnight, you knew she was "normal" when you met her.
Go shopping with her and suggest some stuff that you find appealing. I hope you have $$ because if you want her to wear it that bad enough you are gonna have to pay for it. If my boyfriend wanted me to change my style I would expect him to buy the clothes. If she does not want to change her style and wear what you suggest then you have to respect that and drop the issue.
not a change in hell she's gonna go from normal/lame to red hair... haha you love the wrong girl.
But here's what you can do... talk to her about styles you like... if you see a shirt when you pass by a window in the mall, say "oh that's a nice shirt! Bet you'd look great in it... wanna try it on? for me..." *cue puppy eyes* if she laughs it off, there is no way... but if she agrees, well you're in the right direction. Just gently suggest things you like... maybe she'll come along a bit, but she probably won't have an overall style change all that quickly. Style is who you are. You gotta respect that.
your only option -- and I mean _only_ option that avoids being a manipulative jerk -- is to suggest clothing changes to her once.
that's it. say it once, casually, then drop it. "I think you'd look good in that shirt."
then never mention it again. NEVER.
unless she asks. even then, still be casual about it. "I just thought it'd be flattering." then drop it.
she may not want to change. but if she _does_, your saying it only once will plant a seed. whether or not the seed sprouts is another question. but no seed ever sprouted when someone was nagging it to grow...
How? Get a new girlfriend. If you don't like her "normal" style then you're going to need to find someone that already has this type of style. There's nothing you can do or say to convince your current girlfriend otherwise.