Do not define config entities as token types until we have useful tokens

But what you are using for is something entirely different I think. This would be tokens for *one* image style. You're using it just to "pipe" through the image style selection, which is very different from what other tokens there would do.

So yes, you would have to define one anyway.

+++ b/token.tokens.inc
@@ -64,7 +64,9 @@ function token_token_info_alter(&$info) {
+    // a config entity.
+    if (!$entity_info->get('token_type') || $entity_info->isSubclassOf('Drupal\Core\Config\Entity\ConfigEntityInterface')) {

Lets change it to only do it for content entity types.

People find isSubclassOf() confusing and it might get deprecated at some point. I think we can do a check of $entity_info directly, that is a ContentEntityTypeInterface object (the @var above is strange, can you try to remove that, shouldn't be necessary..)

Looks good.

I think it makes sense to have a simple assertion somewhere to make sure that a token type like Roles or so doesn't show up.

Thanks, committed.