Uploading product images

Im creating a site where a user can upload multiple(multiselect) product images at once.

My question is what would be the the "right" way if the user uploads images that have the same name as the ones that are already in the destination folder.. Should I just override the existing one´s with the new images or just add the ones that have not the same name and skip the existing ones.. perhaps prompt the user about it? Im leaning towards overriding the existing one´s..

Thanks in advance