As a new user, I really love the power and functionality of MantisBT, and the addition of timetracking is a great bonus feature. However, when introducing to colleagues the first impression is that the design is quite garish. I did a bit of work on the CSS using randallj's post
as a good starting point. I have used CSS3 gradients, border radii and box shadows to soften the look and feel without the use of any background images (apart from randallj's search button). A few screenshots below demonstrate the changes and the needed files are in the zipped attachment.
I look forward to the theming ability that is rumoured for version 1.3, but in the meantime I hope this is useful for someone out there.