There's nothing wrong with making your character however you'd like! 100% okay to make them a shapeshifter, give them wings, make them a unicorn dragon hybrid, I don't care! But be mindful when entering them into an rp.

If your character is an angel/demon/wolf/mermaid/vampire hybrid who has the powers of life and death at their disposal, it will get very confusing for your partner to roleplay with, and even harder for them to interact with. It's unappealing to try and rp with someone who thinks their character is God themselves.

Once again, it's okay to make your character however you'd like, just be mindful of the roleplay, the rules, and even the owner of the roleplay's character.

Do not make them the everlasting pity party! If your character has some issues, that's fine! They can be addressed and played out how you like, but once they've gone and had their 15th mental breakdown, it starts to get repetitive and boring. Try to avoid this by focusing on their other qualities, and interacting with the people around them for help. Do not state their issues and then not work towards fixing them.