Blogger Thumbnail Pictures - FAIL!

I've been very frustrated with Blogger these past few days (post entries).  For some reason, it's no longer posting thumbnail pictures correctly.  For example:  It usually uses the first image (picture) I embed, instead it has ended up using my signature at the very end, which I have removed as of lately to test Blogger to no avail. My most recent post (Mr. Moose) is now posted with a thumbnail picture of a linky party I just joined!!  What's going on?  Can anyone help or have any suggestions before I pull all my hair out which I cannot afford to lose of what's already left???!!  Thanks!  -Bev