Dear Khaled: Could you upload a zip file with mIRC's icon resources (and other media resources), so we can access them in their normal format with their full and proper filenames? I know that PE resource extractors can give us the files, but it's all sloppy and disarray.

I would like to do some icon editing and submit for your approval.

Apropos, I also had an idea editing about as minimum about one icon for private windows. So I think this the post in this thread will would be appropriate.
In my opinion, the new icon with a green question mark "?" ‒ (which has appeared in mIRC Beta v7.65.563) is very faded indistinguishable and merges with the background.
What if we change it to an icon with a silhouette of a person?

        ‒ the silhouette of a person was taken from here: person-emoji and person-lg

Just for a visual comparison, what this might look like:

     

This will visually significantly separate the private windows from the channel windows.
Please, do not rush at once throw at me hats, tomatoes and bananas))). This is just one of the proposals for consideration. And of course, you can have your own ideas of how this would look best for the mIRC client.
Let's democratically discuss.

Respected Khaled: ‒ Ideally, it would be nice if we (users) were provided an opportunity on my own to assign these icons for different windows and events using client options or with the help of commands.

It's not a bad design. But I was actually looking at the query and chat icons myself and thought they would look better as a speech bubble, aka, comic balloon. Queries would have a question mark inside, and Chat windows would have an equals sign inside (corresponding to their event prefixes). I think the round ovaly shape would better set them apart from channels to indicate one-on-one communication.

I roughly presented out how it might look and I've seen something similar in other applications. It would be interesting to have a look at this.
Can you create (using the mIRC open client) some kind of project layout in Photoshop and place it here as an image (.png) so we can see your idea?