Some feeds lack a <channel> <image> tag, but do provide a <channel><link>, where usually a favicon can be found. Would be nice if that'd be used. Now, unfortunately, many pages still use the traditional .ico format, which i guess would cause lots of trouble. So, lets convert it to .png. Here

https://www.phpclasses.org/package/3906-PHP-Read-and-write-images-from-ICO-files.html

is a class to do that, but it comes with a special license. I'd do the coding, but would you accept such a PR?
The license reads:

---

• Original floIcon copyright (C) 2007 by Joshua Hatfield. *
• All Rights Reserved *

---

  					 floIcon License

                  Program & Concept created by

Joshua Hatfield
2368 Franklin St.
Augusta, GA 30906
USA
(email flobi@flobi.com)

This document contains the rules by which you can use, alter or publish
parts of floIcon. floIcon has been created by Joshua Hatfield in his spare
time. You are legally bound to follow the rules described in this document.

Rules:

!! floIcon is NOT Public Domain, shareware, careware or the like !!

You may under no circumstances make profit on ANY part of floIcon in
any possible way. You may under no circumstances charge money for
distributing any part of floIcon - this includes the usual $5 charge
for "sending the disk" or "just for the disk" etc. By breaking these rules
you violate this agreement, and hence will be sued.

You may not remove any copyright notices from any of the documents or
sources given to you.

This license must always be included "as is" if you copy or give
away any part of floIcon (which is to be done as described in this
document).

If you publish any part of floIcon, I, as creator, must appear in the
article, and the article must be clearly copyrighted subject to this
license. Before publishing you must first send me a message, by
snail-mail or e-mail, and inform me what, where and when you are
publishing (remember to include your address, name etc.)

Any running version of floIcon must include my name in the login and/or
intitial connection sequence. Furthermore the if there is a credit section
or command in any application using floIcon, it shall always contain my
name, addresses, and a notice which states I have created floIcon.

You are allowed to alter floIcon, source and documentation as long as
you do not violate any of the above stated rules.

Regards,

Joshua Hatfield

Note:

I hope you will enjoy floIcon, and encourage you to send me any reports on
bugs (when you find 'it'). Remember that I am using my spare time to write and
improve floIcon, bugs, etc. - and changes will take their time. I have so
far put a number of programming hours into this project. If you make any major
improvements on floIcon I would be happy to hear from you. As you will
naturally honor the above rules, you will receive new updates and improvements
made to the class.