Where are the menu icons stored?

If you are using TB Mega Menu module in your drupal project then, this issue is reported here. Please try to apply this patch and check.

Additionally, if you are looking for icons then you can find icons from here.

Feel free to ask incase of any query/concern regarding this.

Thanks,
Snehal Brahmbhatt | AddWeb Solution
https://www.drupal.org/user/3147795/track

It looks like you need some programming or theming support. And possibly it's for a contributed module or theme?

Anyway... I'm sorry, but although you can create issues in Drupal Core and mark the category as "support request", we don't really handle support requests in the Drupal Core issue queue as a regular practice (that option is mostly there for filing support issues for contributed modules and themes).

There are several support options listed if you click on "Support" at the top of Drupal.org, which will take you to:
http://drupal.org/support

There you can find out about the Drupal IRC channels, and the Forums, which are our two main support mechanisms in the Drupal community. You might also try http://drupal.stackexchange.com/

Good luck with your issue!