I was going through the forums and didn't see the SM action to change the theme so I thought I'd post them here for the admins.

sm_themes_version
Themes version

sm_themes_enable [0/1]
Enables or disables Themes

sm_themes_next_theme "theme-name"
Forces the next map to use the given theme

sm_themes_announce [0/1]
Whether or not to announce the current/next theme

sm_themes_particles [0/1]
Whether or not to use custom particles

[TF2] Themes v0.8 (Bug Fixes + 1 New Theme) - AlliedModders