I've heard plenty of women are approached by men they aren't attracted to or even dislike.
I'm sure you're not the only woman this happens to.
What you should learn is how to make a good glare/look of anger with your face.
Have a neutral/happy facial expression the rest of the time, but the second a nerdy/neckbeard looking male shows even a hint that he's about to approach you, give him a death stare that will make him back-off before he even opens his mouth.
I hear some women do it ALL the time to some men, so it's not like it's considered rude or mean for you to do it.
That or, y'know, you could just politely say "No thanks" if it ever happens, and then become aggressive only if they don't listen and won't leave you alone.
Yes, from pictures you don't look 'soft' necessarily, but rather 'friendly', and average. I wouldn't say introverted, but more than likely Ambiverted. Very plain and normal, but in a 'good' way. 'Down-to-Earth'. Not likely to chew a guy's head off for approaching (keep in mind since men have to do the approaching, they may encounter rudeness from some women, the worst of which may even insult or put him down directly rather than just politely say no, so the more approachable looking, the better in our eyes).
Honestly, I wouldn't go through the effort of being unapproachable to absolutely everyone, because then it might drive away the one's you're actually interested in.
Goth and alternative women aren't always necessarily rough, tough and edgy 24/7. Some goth women are pretty much just a normal, regular person, but they have love for 'dark' things, rock/metal music, and like the goth aesthetic, so I wouldn't go thinking for a second that you also have to be just as icy, edgy, rough and tough to be accepted by alternative women.
If anything, you may provide a good contrast to punk and alternative women - they say opposites attract sometimes.