Over the decades many characters major and minor have had their costumes or general looks "tweaked," that is, a particular artist or the editorial powers have made a slight change in the way the character is presented visually without making a big deal about it and usually without any in story reason.
For example in the early 90s Todd McFarlane began drawing Spider-Man's costume with far more intricate web patterns (so intricate that when he was drawn from a distance the webbing on the costume was usually left off because it would be too small to render) and made the eyes on the mask HUGE, covering most of his face. As far as I know, it was never explained that Peter Parker changed his costume.
Another even more subtle change was that when John Byrne revamped Superman, He made the "S" insignia much larger on his chest and the blue was made a shade darker. It was a small enough change that the general public probably didn't even notice it.
What made me think of this was looking at some of the art for Captain America: Reborn. Cap had an unannounced, unexplained alteration in his uniform around 9/11 when someone got the bright idea to draw the heretofore subtle chain mail of his shirt as scale mail (a completely different type of mail, by the way).
I hate this look. It looks clunky, uncomfortable as hell and impractical. How would you like to have metal plating in you friggin' armpits while in battle?
Still I do like some of them. I really like the alterations in the Flash costume that mimicked the look of the short lived TV series.
Also, I kinda like bug-eyed Spidey.
Which tweaks work for you? Which don't?
Again, I'm not talking drastic changes or in-story changes like, say, Iron Man upgrading his armor or Thor being reborn with new togs.