If you use IFTTT at first time, you may have the problem, that your applets don't work correctly. That IFTTT doesn't find your photo in the RSS feed could have the reason, that IFTTT doesn't check the enclosure tag of the feed item. But you have two other options to solve this problem and post your photos.
If you don't need the description tag for the text posting you may use it for the photo URL. Therefor you only have to put the URL in the tag:
<item> <title>Your Posting Text</title> <link>Your Link</link> <description>Your photo URL</description> <pubDate>Your pubDate in the RSS format</pubDate> // e.g. "Wed, 21 Mar 2018 09:35:00 +0100" <guid isPermaLink="false">Your unique ID</guid> </item>
Now you can add the ingredient EntryContent in the formular of the Photo URL to your applet.
If you want that IFTTT gets the ingredient EntryImageURL directly, you must add first the following to your RSS feed at the beginning:
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:content="http://purl.org/rss/1.0/modules/content/">
Now you can add content:encoded tag to your items. In this tag you must use the img tag with the URL like the following:
<item>... <content:encoded><![CDATA[<img src="Your Image URL" />]]></content:encoded> ...</item>
Now IFTTT detects the URL of the img tag as EntryImageURL for your photo posting. Then you can use the ingredient EntryImageURL as Photo URL in your applets.
If you have further questions, please write me an e-mail at ed.nnamttug-ppilihp@liam and I will try to help :)