I dont know whats wrong with My Ubuntu but my top panel was gone its proper look .Help me to restore it . i am giving you the sample image .
It's possible that the theme is using a smaller set of icons because of the thickness of the bar, or the icon theme got changed for the theme,if changing themes does not work try changing the icon theme for the theme or changing out individual icons in that theme. So here is an example using the default "Ambiance" theme.
So your icons look similar to this, worse in your case.
Next with that information navigate to
This is where the status icons are, so then you need to select what pixel size your theme is using, from 16, 22, and 24. since your theme turned ugly it may be possible that it is using the 16 pixel icons.
But since you have a wired icon I don't think this is the case, For example the 16 folder does not contain
You can then use
Since it seems that all your icons are dark, I would suggest changing the icon theme from
Hopefully this will give you the basics so you can make your icons look however you want.