Wow!
I am awed. This is awesome. I agree about the pictures being humorous, but that just adds to the melodrama of the song. Remembering those happy times while singing such a sad song makes the song seem even deeper and more emotional. The fact that people may view them as funny is nothing to worry about, that is just people being themselves.
About the jumping Mia sprite, if possible, rather than stopping it from jumping, if you could make it look a little bit more intended then it could be viewd as her crying whilst she is singing. At least, that is what I tried to think of it as, but that could be just me.
Also, I agree that Franziska should not be in it, though the whole Alternate Reality arguement is a good one. I think many would appreciate it more if it was a little bit more realistic, but that is entirely your choice.
Finally, well done. 10/10 and a rating of 5. Fantastic work, keep it up.