Oooo what a great topic,
AquamarineSteph! Thanks for starting it. Trip reports are my favourite kind of topic. I personally will rarely read a report that doesn't have any pictures - they're essential to me. Not only pictures of the people writing (which I also appreciate, but I think they're more of a private thing) but photos of what they're talking about. I'm currently trying to learn photography so I'm more and more aware of the difference between great and poor pictures. I'd rather read a trip report with great pictures and I do avoid those with poor pictures a lot more now as I just can't seem to lose myself into the experience as much.
I'm a foodie, and the first thing I'll do is usually scroll down the first page and see if the OP has included shots of food. If they haven't, it's fine, but I'm a lot less likely to read it. Not only pics but detailed descriptions of mouth-watering food is what makes life worth living. The 'Disney Dining Reviews' section of this forum is my absolute favourite.
My favourite trip reports include tips or what people would do different/do the same, not just at the very end but throughout. I love when people talk about how they planned something, again, not just at the beginning, but throughout. I also enjoy it when they say things like 'this is what we did, however if you're more of a person who likes X, you should definitely do Y, we saw other people doing it and they looked like they were having a blast', so a trip report, with a sprinkle of educational stuff thrown in (if you can call it that).
Last, but not least, I like it when people take me somewhere I've never been and can only dream of or do something that's on one of my wishlists. For example, I read a lot of trip reports that include dinner at the Victoria and Albert's, people who stay in concierge at WDW, concierge level during cruises, and anything
Adventures by Disney.
Good luck with your TRs, they might take a while to write but they're worth it. I love memory keeping and I want to make it more of a priority in the future (hence the interest in photography).