Thanks for your reply Eric.
Here is what I did,
adb push /path/to/my/image /mnt/sdcard/Pictures
It pushes the file to device, Now I want my test case to feed this image file to the camera (which is currently opened in my app) so that my test case can proceed. Is this something possible with Appium, like it gets the current running camera instance and give a particular file as input? something like driver.getCurrentCamera().sendFile("/path/to/the/file") ?
Hope its clear enough.
Sumit