alt attribute for Image tag in html

[voythas]

Scenario:\[code\] <img src="http://stackoverflow.com/questions/15659193/filepath" alt="image not found">\[/code\]This will make sure that if the file is not found in the path then the text would be loaded .....Question:Instead of a alternative text can a image be loaded ?? is there any tags would readily serve my purpose and is there any custom javascript functions which could be given in #alt tag??