I dont know of a why to set a background for the frames within the layout file, but you can use something like Discord or xArt(?) to do it.
The fonts is easy enough, just edit the layout's lua file that you want to use. Find the text elements you want to change (NameLabel, ClassText, HealthText, and ManaText). There should be a Font tag with a reference to the font file. Just change this to the font you want to use. You can use a diffirent font for each text field. Just make sure you link them right. The path for the addon folders is Interface\\AddOns\\ag_UnitFrames\\fonts (you can change the ag_UnitFrames bit to another folder and/or font location).