The <h1> tag is simply part of the HTML language. The skin doesn't "support" or "not support" it - the browsers do. The skin just doesn't use it for anything. For controlling layout and styling, it's a sledgehammer - it goes back to the days before CSS existed. It causes its own default formatting of the text block, which the skin would need to actively undo.

I generally resist "coding for Google" (or worse, "coding for social media"). Each index page does include a meta description tag, though that's the same text for all pages in the album - see the skin's Misc tab. And each page includes a <title> tag, which actually is required for valid HTML. That contains the album title or the folder title - the latter if you choose Titles & Logo > Show folder title in browser tab. And search engine crawlers definitely pay attention to that tag - it's very high on the list, probably higher than the <h1> tag.

In short, the messages you're seeing aren't identifying "errors" - they're just someone's idea of what SEO needs. But every page produced by the skin already includes the information that could also be placed in an <h1> tag. It would just be redundant, and undoing its ill effects would just involve excess code.

Do a Google sesarch for neptune skin jalbum, and look at what comes up in first and second position. My demo albums don't contain a single <h1> tag. Doesn't seem to be a problem!

My understanding is that getting your page to show up in Google searches relies more on having other sites pointing to yours. But attempts to create "link farms" to fool Google are doomed to failure, and can actually cause your site to be penalized.

The standard advice remains: produce interesting content, include good descriptive text, and then just move on.

BTW, the meta decription tag is best used to provide something more readable than the simple page title. For one of my demo albums, for example, it could be something like, "The Neptune skin for jAlbum produces a clean, uncluttered layout for presenting your photos." I haven't bothered doing that, but that longer text would, theoretically, show up the Google search results. The first search result, which points to the skin page on the jAlbum site, shows exactly that. That text - "Download jAlbum skins and give your photo albums any design you want. Endless customization!" - is buried in the meta description tag on the page.