I'm writing a memoir, but I'm writing it in the third person using a semi-omniscient narrator. Is that an absolute no-no or might it be acceptable if the writing and story is superior?(1)
Also, it is not chronological, but most of the chapters/segments could stand on their own -- some are like flash fiction (100 to 500 words) and some are like a short story. They are all intrinsically connected (a somewhat difficult task) and I think I've managed to put the thing together in a way that won't confuse anyone.(2) Is it ever possible to have a photo at the beginning of every chapter?(3)
Let's take your questions in order.
(1) Writing a memoir in the third person is fairly unusual. Oddly enough, I have such a memoir on submission right now. Writing in the third person creates a distance between subject and reader that often defeats the purpose of memoir: sharing the emotional journey of a life.
You might want to do some research here. Find memoirs written in the third person. Salman Rushdie JOE ANTON is one. I'm sure there are others. Read them, and try to assess whether they work. Were you enticed to keep reading? Did you feel connected to the story?
There's no hard and fast rule that memoir MUST be in first person but it's like writing a novel in second person: you've got to be really really deft to overcome that POV hurdle.
And ask yourself bluntly what you want to accomplish by writing in the third person. Unless there's a very specific reason to do so, first person is just going to make your life a whole lot easier.
(2) You're not the right person to assess whether this works. You're entirely too close to the project. This is where you need beta readers, and honest ones. Have them read this. Ask "where did you lose interest?" to find out where the problems are. You ask that rather than "did you like it?" cause no one will say no,and/or "what's wrong" because often people don't know what's wrong. They only know when they stopped being interested or started to skim.
Beta readers are NOT editors. Editors help you fix things. Readers tell you if you've got things that need fixing.
(3) Honestly, probably not. Printing photos in books adds ENORMOUSLY to the bottom line. You can put the photos on your website, keyed to the chapter numbers.
If you publish electronically of course, this problem goes away, but you're limited to those e-readers that do pictures as well as texts. This isn't an area I know a lot about, sorry.
I want to encourage you to think not about how you want to write your book, but how it will be experienced by your reader. You can do anything you want with your book if you don't care if anyone publishes it, buys it or reads it. Chapters that go vary from 100 words to 20 pages can be perceived as awkward and bumpy. Third person POV can make it hard to connect with the narrator. It's not whether you CAN do these things, sure you can, it's your book. The question is do you want to? Consider your reader as think about this.