Discovery API supports specifying a tile in a URL.

chrome/common/extensions/api/experimental_discovery.idl

Index: chrome/common/extensions/api/experimental_discovery.idl
diff --git a/chrome/common/extensions/api/experimental_discovery.idl b/chrome/common/extensions/api/experimental_discovery.idl
index cd31a72e3dc3ffc74a5c219a61aec106d03f6947..35431f6e5f0c0c9c770e01b4c4328b812c91287e 100644
--- a/chrome/common/extensions/api/experimental_discovery.idl
+++ b/chrome/common/extensions/api/experimental_discovery.idl
@@ -14,6 +14,9 @@ namespace experimental.discovery {
     // The linkified text. It should be relatively short.
     DOMString linkText;
 
+    // The url of the image to use as a tile.
+    DOMString? urlImage;
+
     // A score indicating how interesting that suggestion is. The value must be
     // between 0 and 1. A suggestion with score 1 is twice as likely to be
     // displayed than one with a score of 0.5. Defaults to 1.