comments.php: How to display an image through RELATIVE path?

Why are you trying to use relative paths? WordPress generally uses absolutes paths.

Because it’s a theme and not a WP content. It’s a theme for an image gallery, and it could be used by different sites. So I would prefer that all images used by the theme belong to the theme. See what I mean?

If impossible, I’ll keep using the absolute path which will be the image on my own server. I’d just like to avoid that…

Relative paths should work but the images need to be inside the themes folder and not the upload folder. The path would be relative to where the style.css is located.

src="images/imagename.png"
So this would work if the theme’s folder has the “images” folder that contains the image.png

It IS in the images folder of the theme.

Can you change it back to hard-coded and post a link to the site?

Excuse me WPyogi. What is “hard-code” ?

Using the HTML in the template file instead of php (which then generates the HTML)

I was suggesting you try this again:

'comment_notes_after' => '<img style="width: 26px; height: 23px;" alt="" src="images/imagename.png"> Pour voir votre commentaire publié, rafraichissez la page.',

What file path shows up when you use that? Is it a valid file path? i.e. if you paste that file path into your browser, does the image show up?

OK, I just tried it again and I left it that way for now so that you can see.
To be clear, here’s the code I wrote:

'comment_notes_after' => '<img style="width: 26px; height: 23px;" alt="" src="images/attention_w26.png">&nbsp;Pour voir votre commentaire publié, rafraichissez la page.',

Result: the image simply doesn’t show.
Here’s one of the pages in which it should appear (just below the text input area)
https://www.ajwan.net/wordpress/galerie-demo/10-style-diaporama/09-fleurs/fleurs-d-europe/

Then, as you advised, I wrote the image full path in my browser and it definitely shows the image.
You can try: https://www.ajwan.net/wordpress/wp-content/themes/gallery-ajwan/images/attention_w26.png

Now, that line of code is within an “array”. I really know nothing in php so I don’t know it it matters.
That array is generated by ThemeFrame (the tool I make my themes with) and sits at the bottom of comments.php
Here is the full bottom of comments.php:

// The rest is set here:
$comment_form_settings = array(
	'fields'               => apply_filters( 'comment_form_default_fields', $fields ),
	'comment_field'        => '<p><textarea name="comment" id="comment-textarea" rows="10" cols="60" tabindex="4"></textarea></p>',
	'must_log_in'          => '<p class="must-log-in">' .  sprintf( __( 'You must be <a href="%s">logged in</a> to post a comment.' ), wp_login_url( apply_filters( 'the_permalink', get_permalink( $post_id ) ) ) ) . '</p>',
	'logged_in_as'         => '<p class="logged-in-as">' . sprintf( __( 'Logged in as <a href="%1$s">%2$s</a>. <a href="%3$s" title="Log out of this account">Log out?</a>' ), admin_url( 'profile.php' ), $user_identity, wp_logout_url( apply_filters( 'the_permalink', get_permalink( $post_id ) ) ) ) . '</p>',
	'comment_notes_before' => '',
	'comment_notes_after'  => '<img style="width: 26px; height: 23px;" alt="" src="images/attention_w26.png">&nbsp;Pour voir votre commentaire publié, rafraichissez la page.',
	'id_form'              => 'commentform',
	'id_submit'            => 'comment-submit',
	'title_reply'          => '<a name="ajouter-msg"></a>écrire un commentaire',
	'title_reply_to'       => 'Leave a Reply to %s',
	'cancel_reply_link'    => 'Annuler',
	'label_submit'         => 'Envoyer'
);

comment_form($comment_form_settings);
?>

Thanks for your attention & patience, WPyogi

this line contains a syntax error (php code in a string):

'comment_notes_after' => '<img style="width: 26px; height: 23px;" alt="" src="<?php bloginfo("template_url"); ?>/images/attention_w26.png" /> Pour voir votre commentaire publié, rafraichissez la page.',

try for instance:

'comment_notes_after' => '<img style="width: 26px; height: 23px;" alt="" src="' . get_bloginfo("template_url") . '/images/attention_w26.png" /> Pour voir votre commentaire publié, rafraichissez la page.',

alternatively, consider to program the image as background image:
(image laocation has to be in the /images folder of the theme)

code (example):

'comment_notes_after' => '<span class="img-attention"> Pour voir votre commentaire publié, rafraichissez la page.</span>',

css for style.css:

.img-attention { padding-left: 26px; height: 23px; background-repeat: no-repeat; background-image: url(images/attention_w26.png); background-position: left bottom; }

might need fine tuning; not tested.

YESSSSSS !!!
It’s working and you made my day! ?? The first code you gave works perfectly.
Thank yout so much! – and also to WPyogi for trying to help me.