We are using K2 5.2 with SharePoint Online and see no means to select a theme. We'd actually like to establish one of the out of the box themes (probably Lithium or SharePoint 2013) as an initial standard default for all forms, then worry about tweaking the branding later.
Right now, the only option in the Style properties is (Custom), which shall we say leaves too much latitude to form creators naive to UI best practices. I've been through all the corners of the designer and management apps that I could discover and found no option to apply themes to the forms, nor to enforce a default--which is what I really want to do.
What am I missing in my efforts to have our spanking new Smartforms NOT look like ransom notes? ;)
Thanks.
Bob