plz see this two my blog and give review about that.... http://onlywallpaper.blogspot.com/ http://softwaresdownload.blogspot.com/
I would use a lighter background -> dark grey because the pictures stand out way too much behind that background color.
I like your wallpaper blog, very good work, but you may also add some content to get targetted adsense ads. you may need another header for the software blog. Use an image, that has something to do with the topic. I like the green color scheme.