If you want to go all in, check out Eww - it's a lovely over-engineered and super customizable widgets framework that you can use to build a fully custom desktop bar, too. (and needs a lot of more work than waybar to initially set up)
Wallpaper switcher
Depending on your compositor there already might be something implemented that handles wallpaper switching. Maybe check out the super simple wbg application, or have a look at swww if you want a bita lot tons of more features.
General usage tips for someone who only used full fletched DEs until now?