These are just using a wikia sprite image that contains a few of their wiki icons, but we could customize them to something else if we wanted (something more 'Eternal'-y maybe).
I think these look pretty good, but I'm hoping to get a second opinion before pushing something site-wide that affects a ton of existing pages. For an extreme example with a lot of hovers currently, check out the Icaria page.
I added icons through CSS, instead of adding them directly with [[File:...etc]], because the CSS would be stripped away on the mobile wiki skin where I didn't want them to show. Ideally the hover content would only show on the desktop skin anyway. Currently it shows in-line on mobile and breaks the page flow, so figuring out how to hide the hover content on mobile is another project :P
If you get the chance to try it, let me know what you think. If it looks fine I'll add it site-wide. Thanks!