(https://www.simplemachines.org/community/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FKjZzKHU.png&hash=e6a1ca66acb2225bc2e1e235a4eb861affa42571)
change icon close icon and use one <i class="icon-cancel"></i> tag by fontello
(https://www.simplemachines.org/community/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FDc39ifx.png&hash=473fcd0e4c91b30dde60e97bfa6bee791c53a62b)
or can not be?
script.js, you need to change the class there "generic_icons hide_popup"
// Create the div that will be shown
$('body').append('<div id="' + this.popup_id + '" class="popup_container"><div class="' + popup_class + '"><div class="catbg popup_heading"><a href="javascript:void(0);" class="generic_icons hide_popup"></a>' + icon + this.opt.heading + '</div><div class="popup_content">' + this.opt.content + '</div></div></div>');
;) thx
(https://www.simplemachines.org/community/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FbsanyMs.png&hash=5b1d20e46ded2abe5b412a7e5085dfb9ab5505b1)
note : this method is not good for creating new themas
Of course it is good for new themes... It's all handled via css. You just need to use the same basic css as the standard... And add custom stuff for special displays.
Which also means that mods run nicely on all themes...
If it's just images, then adjust the css to point to a different image rather than changing the css tag itself