1) On the wall when you use Upload it is used as an attachment to your post - so if you upload and then just go to other page without posting a message, the image is not posted on the wall and you then may wonder why it didn't. My suggestion is to have a closing event handler for the page that shows a warning message (see what facebook shows) only if the post has attachments or has a non-zero length (some text is entered in the post textarea)

don't remember if the event handler for page closing is supported (or supported in exact the same semantics) by all browser btw, but it's nice to have

2) Also, it seems that when user uploads an image to such a post it immediately appears in the activity stream. If they delete the post attachment it also gets removed from the activity stream. Then if they decide to not post or accidentally don't post (see [1] above) by going to other page, the image remains at the activity stream. So its two issues for [2]:
2a) the image attached to the post should only appear in the activity stream AFTER the post has been sent (user may have uploaded some sensitive image by accident and decided to remove it or not post at all, but in the mean time someone may have seen the image from the activity stream without the user expecting it may have happened)
2b) if user doesn't post the message the image shouldn't stay in the activity stream (solving [2a] will solve this too)