Please increase the value of memory_limit to 500 once on your server and try to upload the images again.
If the issue persists the please create a ticket at https://webkul.uvdesk.com with your Admin login details and FTP credentials.
I would like to recommend you to raise a ticket at https://webkul.uvdesk.com/en/customer/create-ticket/
And please attach the screenshots of the error.
Also please include your FTP details and QloApps back office admin credentials on the ticket so that we can check and resolve the issue.