Early printers where not enhanced enough to support even basic graphics ability and thus characters were used in place of graphic marks. They were mainly used for making banners and ASCII art is also very commonly used amongst software piracy groups to display group logos inside text (*.nfo) files.
So just goto Asciiconvert. Then Enter your image path or upload your picture.It gives you various options like Colored character background,Convert to gray scale,Use white background,Flip image horizontally,Flip image vertically,Monochrome output,Characters to be used in width. Previously I wrote about 11 best Free Picture/photo editors, which you can use for editing Your holiday or Party pics like a professional.
Photo2Text is similar to AsciiConvert but it does not have options like it.Although it allows you to adjust Brightness.You can also get Firefox extension to convert images.
Links : Asciiconvert | Photo2Text