Ah thank you, that should do it. I searched and couldn’t find that ??
EDIT:
For anyone else who can’t figure this out, here it is. Download exec-php (Google it, WordPress Plugin), then the code is:
<?php if (is_single()) { ?>
<img></img> <—- Image for single page here
<?php } else { ?>
<img></img> <—- Image for other pages here
<?php } ?>