That's a hard question to answer since it depends on the person who has the problem. Perhaps you except too much of yourself and put yourself on a difficult position because of that.
The bad thing is that the artblock “feeds” itself if you try to force yourself to draw and feel that you fail time after time. You get depressed/disappointed and when I feel that way I know that stuff I do won't come out well. And so if I force myself the block gets worse.
I had really bad artblock some time ago (year or two, don't remember) and it lasted a long LONG time, I got over it eventually though. This may sound really weird but now I just refuse to get depressed/disappointed about my art for a long times, guess it's sort of self “brainwash” XDD . Personally for me it's about trying to be positive as stupid as it may sound, like thinking “Hell, I can get better but it will take its time” and even if its just tiniest little thing but I realize there's something that I have improved in doing I go like “HELL, I've gotten little better, YAY”. Things I do don't nearly always go as well as I wished so try to take it easy, I know if I start to dwell in it it's gonna be bad. Sure I may get little slopes but nothing major. Hehe, THOUGH I still have pretty bad problems with colors, but I'm working on it.
Though there are some little things that might help like music, I saw you writing that you already listen music but what about something completely new, perhaps even something that you might not listen otherwise? Not necessarily for while you're drawing but just because. I know this is easy for me to say since I like really wide range of music and I'm always looking for new music XD, but it's worth a try if you haven't yet.
You could also see if you find something inspirational from somewhere, other artists, nature, cities, books, games, movies, machinery, clothes and all sub categories of those subjects and more, eyes and mind open. Go wild. Some of those things work fine for relaxing too which is important.
Of your suggestions fanart might help, even requests BUT only things you feel like doing. Don't force yourself to do something you hate/don't like.
You could try and do something you don't usually do. Something overtly cute or something really ugly, something abstract or draw animals real or fantasy. (yeah, I dunno if you actually do something of these things but anyway XD ). Maybe something where you don't have to think at all, like sometimes I do these abstract squares, cubes and shapes, completely without thinking and it's kind of relaxing. But if you feel like it’s forcibly done it might not be the best thing. Perhaps just scribble mindlessly or not so mindlessly and something could come out nicely. Not everything has to be strictly for practice.
Traditional isn't horrible option once a while XD , it might give inspiration too.
Sometimes it's good to take a little brake like a day or two to clear your head. It doesn't have to take long. Read a book, listen lyrics, watch a movie, play a game, sleep, anything. OH sleep reminded me, I dunno if you have usually a lot of dreams but they can be real inspiration too if you remember anything from them.
And you know it's not ABSOLYTELY must to choose between some specific styles like manga/cartoon, semirealistic or realistic, you can do what you feel like when you feel like. I don't believe it's a bad thing. I actually think it's wonderful that one person has more than one style. But then again that's me X) .
Take it easy and don't be too hard on yourself, being critical to oneself is good, but not to the point when it goes over the top and hinders you <3
I agree with you. And I think I'll solve the problem doing fanart or making no so complete artwork, cuz I'm at the point that I find really frustrating to use colors make a painting. I love to make sketches using references. That's it..but sometimes it's like I'm not evolving, so I find useless to sketch because is a thing I think I'm good at. But it isn't useless at all, I know :°(