There is definitely something going on in this post http://circleinteriors.wordpress.com/2012/11/13/skandi-stars-stripes-toy-box-120/ where there are only 5 images in the Post, but for some reason there are additional blank thumbnails showing up in the sidebar.
I'll tag this for Staff assistance; please be patient while they get back to you.
Also, how are you inserting the single image in each post? Do you insert each individually and set the alignment to Left or None? Some of the images seem to be too large for the accompanying text and thereby knocking the Gallery below it out of alignment. (example) Perhaps you could try with a smaller image or by resizing the inserted image to see if that corrects the alignment for you.
The Gallery in your theme does have a colored background by default. See this post in the demo site for comparison. http://ideationandintentdemo.wordpress.com/2011/07/07/fall-in-luxembourg/#
Unless you are using a Custom Menu, all published Parent Pages should appear in the theme's Navbar automatically. See here for more info on Custom Menus: