A few arbitrary tips on Omeka-S theming.

Retain existing classes on analogous elements as far as possible, as they are sometimes referred to by internal Omeka CSS classes. Obviously you can imagine edge cases where this isn't desirable. But it's a good first rule to follow. Obviously if you omit some design-element entirely you must also omit the class associated with it.

In a similar vein, be wary of doing less than the requirements of a theme. There's no real verification or way of testing that a theme handles all paths sensibly and in a manner consistent with the expectations of the user.

For example, there are certain site settings your theme should support: "embed media on item page" is a site specific setting that you must handle within your theme, but there is no validation that your theme does in fact handle this.

Do not ever use <p></p> elements in your module markup. Use custom divs or spans with your own classes. Why? The Html blocklayout generates <p> tags, so any attempt to style page text will often inadvertently style your more-irregular p tags.

Config form names should be in snake_case.