One thing is if your using the Oxwall CS Image Slideshow plugin. Its best to keep your images to 250x250px and not go beyond 8 images. As that can slowdown the loading of a page.

Then the IP blocking plugins all have a resource problem, they could slow down a site.   

Third party widgets, too many or a very slow bandwidth on a widgets source will slow page loading. In the case of not being able to delete an image that could be a browser cache problem and solved by clearing its history.