Yeah this is the template I use. As I say - its like, ~20 lines of boilerplate:

http://josephg.com/canvas_f.zip

I tell people to leave the html file alone and edit the javascript, using the canvas API to make it draw whatever they want. Canvas supports text, shapes and images and translations / transformations. If they want, I show them how to animate their work as well.

People make fun cursed things like this:

https://home.seph.codes/public/niamh/

Another option is to use the p5.js library. They also have a nice online editor, at https://editor.p5js.org/, which makes it easy for students to get up and running quickly.