Install the official E16 themes using x11-themes/e16-themes

Packages describing “themes” as local USE flag

Package “themes” Flag Description
x11-wm/e16 Install the official E16 themes using x11-themes/e16-themes
mate-base/mate Install MATE Desktop's themes; if you use other themes, you can disable this to spare some space and time.
x11-themes/gtk-engines-murrine Pull in themes via x11-themes/murrine-themes
games-arcade/lbreakout2 Install additional themes
app-emulation/wine-staging Support GTK+:3 window theming through Wine-Staging
media-gfx/album Install optional themes
www-misc/xxv Enable more themes via x11-themes/xxv-skins
x11-wm/pekwm Install additional themes
sys-boot/grub Build and install GRUB themes (starfield)
www-apps/wordpress Installs themes (including default theme)

All packages providing a “themes” USE flag (3)