TK 8.5 added a fabulous new feature (and set of procs) called TTK which give a modern look to tk widgets. But they forget to give an easy way to change the default theme ! So most people doesn't even know they can change how TCL/TK or Python/TKinter applications look.
Here it is, TTK theme chooser is just a little window to choose and set the default TTK theme on linux.
./configure
make
make install
(sudo make install if you're not root)
For Arch Linux users, package ttk-theme-chooser is available on the AUR
Installation is optionnal, you can simply do tclsh ttk-theme-chooser.tcl too.
Just type ttk-theme-chooser in terminal or find TTK Theme chooser in your desktop applications menu.