I'm sure you've seen those lists where the anime is accompanied by a cover image. Hell, maybe you've got one of them.
In order for those lists to work, CSS has to specify the image for each individual show ID. There is no getting around this. That's just the way it is.
Anyway. Moving on.
I've written an online service that will do that for you on the fly.
If you would like to know how the URL is configured:
You will see there are 3 parameters to using the service. USERNAME -> Replace this with your username. This is required. LISTTYPE -> Replace this with either "anime" or "manga" to specify which list to generate. This is optional and defaults to anime if this is omitted. COVERTYPE -> Replace this with the cover type your list requires. All six of the common selectors are accepted. The options are "more", "more-after", "more-before", "animetitle", "animetitle-after", "animetitle-before". This is optional and if omitted it will default to the "more" selector. From what I've seen, the "more" selector is the most common, so if you didn't design your list and are in doubt that's probably what it is. That said, I recommend finding the designer's post and finding out what they say you need.
The order is important. Also, all preceding parameters must be filled out to access one "further along" the URL. For example, if you wanted to set your COVERTYPE, LISTTYPE would also have to be filled out, even though they are both optional.
Otherwise, you can simply go to the MALUtils homepage here: https://viaware.ca/malutils
All you have to do is enter your username and the list type and it will give you the correct URL.
The CSS returned is a completely custom list of your anime/manga covers, tailored just for your user.
This becomes especially useful if you directly import that URL into your list. Every time someone visits your list, it will make sure that the CSS returned is representative of the anime/manga in your list. So you can add a new entry, and it will automatically start to include it in the cover image list. No additional work required.
It's running on the server that also hosts my website. I have so much extra bandwidth and server resources available that just aren't being used. I like using things. So. Yeah.
Go ahead. Try it out. Nobody's stopping you.
Questions you may have
Why isn't my change appearing immediately?
Your CSS will remain cached on the server for 1 hour. As such, it could take up to that amount of time for changes to propagate. This is to help keep the speed up and not hit MAL servers so much. I might change this time span in the future, perhaps to half an hour or something. I'll see how things go. If you would like to clear it immediately, you can manually clear your cache by going to the homepage and clearing your cache. It will clear both your cached anime and manga list. Again, you can find that here: https://viaware.ca/malutils