1. Custom Templates
You'll most likely want to delete custom Templates for any pages that might have them and then remake them if necessary. Of course, before doing this, check the template for any custom code that might be necessary when remaking the template.
2. Featured Content Sliders
Featured Content Sliders are by default used as background images, not actual sliders with text and links attached to them. This also means images should not have text in them as the images will be differently sized according to the user's screen size.
Keep in mind our premium themes have slider blocks available, they're just not the default setting.
3. Background Image
Except on the Donation V2 page, a site's Background Image shows up as a full width image just above the footer. It will have Facebook and / or Twitter widgets overlaid if they're connected to your site.
4. Header Image
Header Images are not utilized in our premium themes - they are, instead, used in our email templates. Typical Header Image functionality is replaced by Featured Content Sliders (see #1).
5. Homepage Tag
On Impact, tagging a page homepage will make it show up on the homepage. In our themes, this tag becomes layout homepage.