I saw this one: [XenCrea] Header & Background Evolved [Paid]. Not sure if it does what I want as below:
I would love to have an addon which can apply the background in logo block, with the ability to display different background on different dates automatically (using cron?) e.g. show Christmas themed background on 25th Dec every year, New Year themed background on 1st Jan every year, etc, automatically. Those dates that were not specified will then show the default background.
It's okay to be a paid addon if someone were to create this.