Is your nextcloud web ui reachable via cloud.domain.xyz or cloud.domain.xyz/nextcloud?
Your settings are not consistent there, but might not be related to the errors.
Missing images were the case in combination with pretty URLs and theming in the past. This error was fixed in between, but in your special case it might be worth trying to remove pretty URLs (remove htaccess.RewriteBase from config.php) and/or try to disable/enable the theming app. Just a guess in the blue 
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