How are you attempting to upload the images to your hosting account?  One of the most common causes of images being corrupted upon upload to the server is uploading the images in ASCII mode instead of Binary mode (this can be set in your FTP client).  Have you tried deleting the file and reuploading it to your account, ensuring it is set in Binary mode?

Have you tried loading the images (on your PC) in your browser, to make sure they weren't corrupted somewhere? This would be something like "File > Open File..." and select your image. If they pass that test, you must be still uploading them in ASCII mode. Are you using some FTP client or are you using cPanel's File Manager? I've never had to manually specify the mode with either, but who knows. The file extension is ".gif" and not ".GIF", so the client can recognize the file type? Are you uploading from Windows, Linux, Mac, or something else? If Linux, you'd probably want "binary" mode for all files, not just images and other binary files. You're not trying to edit the files on the server (in File Manager)? And of course, after uploading a new version of the file, you cleared the browser cache or forced a reload of the file or page (Ctrl-F5) so weren't looking at a bad, cached version...

Both "logo.gif" and "button_subscribe.gif" look fine now. They failed before but are now OK. Be sure that you refreshed your browser (cleared the cache or pressed Ctrl-F5) so you're not looking at an old cached copy.