1.Do you model your characters after yourself or your demographic in any way?
Sometimes; depends on what the character is being used for, or where they stand in the hierarchy. Making an alpha-personality loner, or a shy low-ranking female, etc. It depends on the context for some. For others, like my more long-standing characters, they're who they developed into through the roleplay(s), and the events within, give or take an appropriate backstory (which I enjoy creating, lol)
2. Do you believe that this form of representation in characters is important, even if unrealistic or impractical? (ex: gay/trans animals, cultural aspects in roleplay, etc.)
It can be for some people, but for me, a character is not me. I have a clear difference between the two in my head when I'm roleplaying, so though I have some similarities to how I approach things as my character might sometimes; and others it'll be entirely 180-degrees different from how I would do something, for example.
I think a lot of people can't always separate their characters from themselves when rp'ing, and it leaves a bit of a problem when there is conflict in or out of the rp when someone feels like they're being 'attacked' by another person/character, when it's about what the character did, not what the person did, or sadly, vice versa, and that's where a lot of OOC "drama" comes from, that blurring of lines.
3. Are there any patterns in making your OCs? Are there certain traits that you may or may not see in yourself that you often include in your character design?
Character-wise, I tend to use male characters, though I am female, myself. No, I'm not gay or bi, or anything like that, it's just a preference I fell into once I started rping on a regular basis. Usually my characters are on the large side, whether female or male unless sizing is required by the roleplay, and even then I like to be on the large side of that scale. I am not large, nor am I male, so that'd be counted as antithesis of myself. lol
I generally rp in realistic/semi-realistic groups, so my presets/designs tend to lean that way. I have been in a couple fantasy-type groups where I'm able to have a bit of fun with design though. (if you're curious, I have them on my dA page - linked in signature). I favor darker colors for the most part when it comes to canines, and for felines it depends on what species or setting they live in or are from back-story wise.
Personality-wise, I tend to have confident (sometimes overly-so) loner-type males that have an odd sense of humor to make them interesting. Either that or they're quiet, closed off, observant (which is much more my own personality), and have issues becoming friends with others easily. Again, a lot depends on the backstory that I write for them. No, not all of them have the standard-issue sob-story. lol; one or two of them have [bleep]near novellas though. lol