pyramid static view and file upload
This sounds like your browser is caching the images. Try setting the cache_max_age=0 on your add_static_view, or viewing the page in your browser's incognito mode where it'll use a different cache.
I created new directory via 'myimages' under static directory. And whenever user upload files, file get stores in that directory. Once file uploaded I can access that on html using '/static/myimages/imagename.png'. It works fine whenever I am uploading new image. But whenver I try to override image. It shows me old image only.  
I manually check in directory. It has new image, but still when I try to access that via browser, it gives me old image.