This is a list of examples of positive examples of trans people over time in media. Although it is incomplete now, it will be expanded on over time
The Rocky Horror Picture Show
This 1975 film was the first to have an openly (and proud) transsexual character take a heroic role as she opens up the eyes of characters Brad and Janette to the beauty of sexually. This movie was the first of it's kind to be loved by young people of all genders and sexualities and remains a classic to this day.
Not only was Steven Universe the first children's cartoon to have an openly lesbian couple, but it's also the first to have a non binary trans character, named Stevonnie, who characters openly refer to with the pronoun 'they'. Now one could argue that this is because they are a fusion of two characters, Steven and Connie, however, other fusions (such as Garnet, Opal, and Malachite) are all addressed by female pronouns. It may be that Stevonnie is a demigirl (hence the more feminine appearance) or is genderfluid, or anywhere in between!
Modern Family recently made history in 2016 by having the first transgender child actor appear on the show.The young actor's name is Jackson Millarker as Tom in the episode 'A Stereotypical Day' or S8E2.
In the 16th episode of season three, Glee features an African American trans girl by the name of Unique. She transitions into the true person she is on stage, with the help of Kurt and Mercedes. Unique is played by an actor from the sister show Glee Project, who regulatory sang in drag.
El Goonish Shive
Assigned male is a webcomic by a trans girl by the name of Sophie Labelle. The main character is usually a trans girl named Stephie but this can vary from comic to comic. There are minor characters who are non binary, trans men, and everyone is all of sorts of different sexualities. This progressive comic teaches about not only trans issues, but other gender politics and LGBT issues, as well as other minority related issues as well. This comic is in English, but translated in French and German.
Undertale (2015) was a game that revolutionized LGBT representation in video games by including a lesbian couple as two of the main characters, a trans character, and three non binary characters.
Mettaton, firstly, is a robot who was female at birth (as seen in his room back when he was a ghost) but identified as nonbinary for a short period of time (hence the ghost "Happsta" who eventually transformed into who we now know as Mettaton) and was reffered to with the pronoun 'they' by several characters. Eventually, with the help of his friend Alphys, he gains his true form (Mettaton EX, his robotic non-rectangular body), saying it's the form he has always wanted.
Frisk, the protagonist is most likely genderfluid, but could be non binary or agender as well. Throughout the game, the young human is referred to with the pronoun 'they', unquestionably by all of the other characters. It is said that this could be because the other character do not know the human's pronouns, but there's no reason to believe that when Frisk befriends everyone to the point of where they should have that knowledge.
Like Frisk, the game indicates that Chara is most likely non binary, genderfluid, or agender. However unlike Frisk, the game seems to indicate that the most likely of these is a non binary gender when chara says "HP. ATK. DEF. GOLD. EXP. LV. Every time a number increases, that feeling... That's me. "
Lastly, there is Napstablook, a non binary ghost who is only referred to with the pronoun 'they.' They are also Mettaton's cousin, and really seem to look up to the robot.
Magical Girl Rising Project
La Pucelle is a trans girl, who always wished to be a girl without knowing that she could be, and finally gets her wish granted when she becomes a magical girl. You can tell she really hated being 'stuck' as a boy for so long, by the way she insists that Snow Wight refer to her with her magical girl name as opposed to her birth name and wants to be addressed with female pronouns.
In S4E13, there is a character by the Name of Baby Snaps who says she wants to become a princess [just like Princess Bubblegum] to which she is met with only laughter, therefore humiliating her. Baby Snaps clearly wants to be a female, but is treated like she is crazy for this. She ends up going legitimately crazy trying to become a princess and attempting suicide. The entire episode is a very clear metaphor of gender dysphoria and the consequences of the lack of acceptance from mentors and society for being who you truly are.
Davepetasprite^2 is canonically non binary, but most likely bigender. They, like Stevonnie from Steven Universe, are a fusion of a male character and a female character (Davesprite and Nepetasprite respectively), but have canonically discussed gender and came to the conclusion of preferring neutral pronouns.