Go to Settings > Appearance > CSS Snippets and add one with the following content:
```
.workspace-leaf,
.workspace-tab-header-container {
background: transparent;
}
.workspace-split.mod-root,
.workspace-split.mod-root .view-content,
.workspace-split.mod-root .view-header {
background: transparent;
}
.view-header-title-container:not(.mod-at-end):after {
background: transparent;
}
```
Enable it, then make sure you have a wallpaper ;)
I personally use [Wallpaper Engine](https://www.wallpaperengine.io/en) for the wide selection of wallpapers and animation capabiltiies!