Well, there are lots of funny memes and pictures on Nairaland. If you're using Opera Mini mobile browser, you'll realize that when you long click on a picture you wish to save, and eventually download it, when you get to your download folder, the file is saved as an unknown format.

At that point, all you need to do is to simply add an extension name to the file. Just rename the file, and add .jpg to the end of the file name. Click OK and viola, you have your pic.