Local motifs?

I noticed that a lot of cms and forum boards can easily be "themed" or change motifs. Has anyone done this for drupal? Maybe a simple token icon on the upper left and a background color changer. One for each local holidays like Christmas motif, Ninoy Aquino day, Independence day motif, etc. Just to add a little more pizzazz every now and then on my dull stock garland themed site ... 8-)

Advance apologies if this is a stupid or awkward question. I did several searches on the Drupal site and none came out relevant to my inquiry. I most probably did not know what proper keywords to plug in. All theme modules looked like overkills for this simple task since I did not want to change the drupal layout but simply wanted a simple way to add a "motif" or "skin" to my rather dull site.