Absolutely - it makes it more interesting for any blog but given that the topics are photography then having an image is a must.
I agree! If the goal is to focus the user's attention on the photo, then it should be the main one, but the signature will also not be superfluous.
You should add more than one photo to your blog post to increase SEO rankings. Be sure to use a program such as Gimp to shrink your image size so your site will load faster.
Of course you need to use photos in the blog. Then the site looks more attractive, and this forces new visitors to stay and read your posts. Now there is a lot of competition and a great variety of different blogs, so the page should be attractive so that more readers are interested in it. It's just human psychology. If you do not like the product label, it is unlikely that you will buy it. Or, for example, children are more willing to choose books with bright pictures than without, because it is more interesting. The same goes for adults.
Hey Master-Yoda, not sure if this will be relevant to yourself, but making sure pictures are not too big will help your blog to load much faster for your current and any potential visitors to your blog. Also, from an SEO prospective images should have 'alt tags' so at least the search engines know, 1) you have a good site i.e., loads quickly and 2) the search engines will actually know what all your images are about. Hope this is applicable and of some help. Thanks Harvey.