How to delete podcast art from defunct podcasts

I download lots of podcasts onto my iPod Touch. Over the years, some of the podcasts have stopped, so there are no more episodes. Yet, the podcast art still appears on my iPod. None of them show up in iTunes, on my list, but they are ever-present ON my iPod. I can only delete art from current (existing, functioning) podcasts. If I search for the defunct podcast name within iTunes, of course there is no such podcast. I can't do a darned thing from the iPod. How do I get rid of it? Today I logged out, logged in with a different apple ID, logged out, then logged back in as the ID I prefer to use. In the process ALL my podcasts were deleted. On the IPod, there was nothing there - no podcasts, no art, period. Yet once I began subscribing again to my podcasts (the ones I know are still updating) it brought it in all of those, but it also brought in all that artwork, with no podcasts for the defunct programs. Help!