Unless your organization has prohibited this, Microsoft Teams has the option to upload and use a custom background to enlighten your conference call or for some comic relief.
Lots of companies made pre-made background sets available, varying from TV shows from the BBC, franchises such as Star Wars, to retailers such as Ikea or LEGO. If you are in a retro mood, you can also check out the MS Paint themed backgrounds provided by MS here.
However, nothing is as fun as creating your own, especially if you put some work into it to make the blend more natural. What I mean by that is try to make sure the perspective is right, that you are seated such that it could be you sitting on that chair, etc.
Below are some of my other custom backgrounds for you to download and own personal use.
Together mode is meant to impose the attendees over a background representing attending class or other events.
Another fun thing to do is selecting a static image containing a person after covering your camera. The following pictures can be used for this purpose.
Disclaimer: Images reconstructed and elements re-used under fair use. If you feel an image does not belong here, please contact me.