As stated in my comment(s), marking a question as a favorite, by clicking the star below the arrows for up- or downvoting is a solution. Later these can be listed by the user. This a good system to show at the same time that the question (or an answer to it) was particularly valuable for a user.
the boxed number shows the positive votes received by your answers. You can see it by placing the mouse cursor over the number for a couple of seconds:
this is what happens after hovering the number 4.
In your screenshot the user has never answered any question, so all tags have zeros. He gained rep only with questions, not answers
It seems that the Imgur system, which is now used for the "Uploaded picture" option in your profile page (see this link), does not support .png with an alpha channel. Every time I've tried to upload one, it was rendered with a white background on TeX.SE:
I was misled by this 2008 discussion about Gravatar's discontinued support for .png with an ...
User profiles are granted as much liberty as possible, but there should be some common sense in terms of the content being posted there. User profile pictures especially, since these make their way into the mainstream site content more readily than the description (in the user flair).
If you have reasonable doubt as to the social acceptance of a user ...