Look at the URls below:
Capturing Video on J2ME devices http://www.java-tips.org/content/view/839/73/
Displaying Image from Servlet on J2ME device http://www.java-tips.org/content/view/1006/73/
The example in above URl will give you idea of capturing image from mobile in byte array.
The example in 2nd URL is downloading image data as byte array from webserver, which is exactly opposite to your needs, but I think you can get an idea of how to downlaod/upload data from MIDLet and web server.