> Do other people see actual images when they imagine something?
Pretty much.
In my case the image is not very clear around the edges, but it's very sharp where my mind eye is directly looking at. The rest is a bit blurry and fluid, but the general spatial structure is still clear. I do see color too.
It doesn't actually feel like literally seeing. It feels more like the post-processing your brain does after the real sight is processed. I can even mind-see with my eyes open and it feels different, which suggests they're separate mechanisms. It feels kind of like a projection in the back of my mind.
I'd compare it more to remembering sight, with the ability to mix those memories and imagining them (e.g. I've never seen a pink elephant but I can mix elephant and pink color).
For more intricate shapes like people's faces everything is fluid and not very sharp though. I get the rough shape of their heads and obvious details like the hair and then I can focus on specific parts of their face but not the whole picture. I've never been very good at remembering faces, but I'm very good at recognizing faces (even strangers which I just happen to cross on the street), which also suggests those are different brain mechanisms too.
Memorable faces like Angelina Jolie's are easier to picture as a whole, but common faces are harder to picture, no matter how much I've seen them (it's easier to picture Jolie than my own mother).