1. Is there a way to change what picture shows up as the main image for each sub gallery on the main gallery page?? Looks like it just defaults to the first image of the subgallery, but is there a way to set it to a specific image permanently??
Yes. Edit your gallery page, go to the 'Images' tab and select the image you want to use for the thumbnail on the gallery index page in the 'Index' column.
2. Is there a way to set my site header text to always go back to the main index.php page no matter what sub page it is on?? Currently it seems to work that it just refreshes whatever page is currently being viewed, but I'd like that main header text to always default back to the main page.
Yes. Go to 'Site -> Site Settings' and enter the URL you'd like to use for your site header in the 'Site -> Site header link' input field.
3. I really love the page footer links for social media that y'all have pre-setup, but as an artist I'm going to be getting an artstation page set up as more and more in my field are beginning to have these pages, and showkase currently does not have one of these footer options pre made for that. How can I go about adding a similar artstation logo and link along with the other page footer URLs I currently have active?? Is this possible??
The sharing icons that Showkase uses are characters in a custom font (created by the IcoMoon app).
If the IcoMoon library had an ArtStation logo, you could maybe have added it to the font that Showkase uses, and change the logo for a sharing option that you do not currently use.
However, there does not appear to be an ArtStation logo within the IcoMoon library so you might have to just manually add an image link to your page's footer.
You can add custom HTML code to your footer by opening your 'showkase/_themes/base/pagetypes/basetheme.tpl' file in a plain text editor and modifying the {block "footer"} ... {/block} section at the end of the file.