add image to my custom theme with manifest.jsn

 "manifest_version": 2,
 "version": "1.0",
 "name": "Animated Kimi no Na wa",
 "theme": {
   "images": {
     "additional_backgrounds": [
       "images/your_name-cropped.gif"
     ]
   },
   "properties": {
     "additional_backgrounds_alignment": [
       "center center"
     ],
     "additional_backgrounds_tiling": [
       "repeat"
     ]
   },
   "colors": {
     "toolbar": "rgba(31, 34, 61, 0.24)",
     "toolbar_text": "rgb(180, 201, 240)",
     "frame": "rgb(8, 11, 33)",
     "tab_background_text": "rgb(255,255,255)",
     "toolbar_field": "rgba(54, 58, 89, 0.69)",
     "toolbar_field_text": "rgb(255, 255, 255)",
     "tab_line": "rgb(205, 35, 185)",
     "popup": "rgb(31, 34, 61)",
     "popup_text": "rgb(215, 226, 239)",
     "popup_highlight": "rgb(205, 35, 185)",
     "popup_highlight_text": "rgb(180, 201, 240)",
     "tab_loading": "rgb(205, 35, 185)",
     "ntp_background": "rgb(42,42,46)"
   }
 }

I have been trying to edit a preexisting theme from mozilla store by using [https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/theme#images this link]. I was wondering whether there was a way to make a section other than the top header an image, because in the colors bit I can only add rgb or css color string. Here is the code just in case: { "manifest_version": 2, "version": "1.0", "name": "Animated Kimi no Na wa", "theme": { "images": { "additional_backgrounds": [ "images/your_name-cropped.gif" ] }, "properties": { "additional_backgrounds_alignment": [ "center center" ], "additional_backgrounds_tiling": [ "repeat" ] }, "colors": { "toolbar": "rgba(31, 34, 61, 0.24)", "toolbar_text": "rgb(180, 201, 240)", "frame": "rgb(8, 11, 33)", "tab_background_text": "rgb(255,255,255)", "toolbar_field": "rgba(54, 58, 89, 0.69)", "toolbar_field_text": "rgb(255, 255, 255)", "tab_line": "rgb(205, 35, 185)", "popup": "rgb(31, 34, 61)", "popup_text": "rgb(215, 226, 239)", "popup_highlight": "rgb(205, 35, 185)", "popup_highlight_text": "rgb(180, 201, 240)", "tab_loading": "rgb(205, 35, 185)", "ntp_background": "rgb(42,42,46)" } } }