I find all of those examples of photos very helpful.

Doesn't really matter. An easy-to-see photo of the toy itself is great for me. I don't find every side of the box it came in neccessary in a review. One simple shot of the box is fine. I prefer reading or seeing other photos of the toy, not the box. There have been instances where seeing a toy next to another was helpful, but not neccessary. Also, sometimes smaller toys next to an everyday household item can be nice if it's hard to tell the actual size. One I had a toy the same size of a bic and I used that photo in my review to show just how small it was.

Measurements and arrows don't get noticed by me. My eyes just look right over that. I guess the absolute most helpful way to show a size of a toy for me personally, would be in your hand. Simple and effective.

any of those options would suit me just fine.

A toy in the hand, or next to an everyday item is great for size. Rulers are less helpful for that. I know hands aren't uniform in size like rulers are, but it's the experience most of us will have with toys - either seeing them in our own hand or the hand of a partner. So I find that the most helpful of the size estimate type of photos.

If the reviewer owns several similar types of toys, I love to see photos of them together, as I might be trying to decide which of several toys I should get next. Or I might already own one toy and be trying to figure out if the reviewed toy is too similar to be worth the expense.

A toy in hand isn't helpful to me. Hand size varies so much, and it gives me no real idea how big a toy is.

All the other things you listed though? Definitely helpful.

Next to every day items. that gives me the best idea on size

Everyday items and handheld really give me an idea of the size. All the ones you listed are helpful.

I personally find that an item next to a ruler is really, really not helpful at all. Sure, it shows length, but, that's about it. I can find out the length from your review, hopefully.

Hands, also, not super helpful, since hands vary in size. My hand is very large for a woman, so, it'd be very off for people.

I like the pictures with the measurements on them, especially if it's a bulge-y/swell-y toy that has varying diameters. I sometimes like seeing the toy next to other toys that are similar, but, it's not super helpful if I don't own any of the toys.

I like pictures with rulers or measuring tapes as well as actual written or typed measurements (with or without arrows). I also like when the toy is shown next to common objects (soda cans, dollar bills, etc) and other toys as well. I don't find hands particularly useful because size varies so widely, and non-standard objects are also not useful to me because if I don't have the exact same object, I have no reference point for comparison.

Next to everyday things isn't always helpful, because I'm in Australia and sizing of products is sometimes different here. That said, if it's fairly internationally universal like a CD or a aluminum can, then it's a pretty helpful.

Rulers and measurements with arrows don't help much.

Next to toys of a similar type is only useful if I own or am thinking about buying one of the other toys pictured.

Hands vary in size, but you can generally get a basic idea of the size from such photos so I find them really helpful.

I like to see actual measurements of all the different parts of a dildo/vibrator, a toy placed next to a soda can or water bottle for size comparison, close-up pictures of special features (on toys or lingerie), and lighted up picture of a toy (if there's such a function).