SnackAmp supports cover (album) art for both the GUI and the web server. Cover art for SnackAmp is simply an image file stored in a folder. Typically you keep folders unique for one album, so it make sense to place an image file in there that is the cover art for that album. The standard now-a-days is to store a file called folder.jpgor folder.png in each folder that is a cover art image for that album. However, if the folder is for an entire artist you can save an image of that artist, there are no restrictions.
You can change the dimensions of the Cover Art in the Album display using the Desired Cover Art Height setting. You can also choose to display or not display cover art in the main player window and whether to show it full height or the height of the track info display. You can also toggle cover art for the mini-player.
The AutoPlaylist can toggle the display of cover art for the currently selected folder using the icon.
The remove web browser cover art can be set to a specific dimension under the Web User Interface tab Display Size setting.
When viewing cover art you have two additional functions you can perform. By double clicking on the cover art viewer, a query box will pop-up that allows you to query goggle image search and Walmart for that album/artist. You can optionally refine the search in the pop-up dialog. When the web browser shows images, you can drag an image over the cover art viewer which will drop the image into the appropriate folder. You can also drag cover art images over the AutoPlaylist folder or cover art window to create an image for that folder. If an image already exists, you will be prompted to overwrite it.
There are also a number tools on the internet to download cover or album art based on the ID3 tag information. They all assume you organize your tracks one album per folder. You can Google for terms like "cover art downloader" or "album art downloader". albumart-qt is my favorite.