Even you click delete button, the deleted images may remain visible in your web browser (only to you) because the data has been cached.
Please refresh (reload) the page several times or clear the cache of your browser to solve this issue.
- [Google Chrome] Delete your cache, history, and other browser data - Chrome Help
- [Firefox] How to clear the Firefox cache | Firefox Help
- [Microsoft Edge] View or delete browsing history - Windows Help
The following command is an easy way to do a 'hard refresh' and force the browser to clear cached data.
Firefox: Ctrl+F5 / Shift+reload button
Chrome: Shift+reload button / Ctrl+Shift+R