he Tango icon theme's goal is to make applications not seem alien on any desktop. A user running a multiplatform application should not have the impression that the look is unpolished and inconsistent with what he or she is used to. While this isn't about merging styles of all desktop systems, we do aim to not be drastically different on each platform.
Along with a generic type fallback, having a similar style will help in the transition phase with some legacy icons which may still remain on a user's particular desktop.
Pretty color pallete.