I've noticed that sometimes, less significant background cars are sometimes added in the comments of movie/series pages on here. The pics are small in the comments, but clicking on them opens another tab where the full-size image is seen. How do I do this? When I try (with IMG tags), the image is super-sized in the comments. Not sure what I'm supposed to do.

Do it like this:
[pic=16833/(picture name here).jpg]

Ah, thank you!

You have to upload them here: http://www.imcdb.org/upload.php first. The code is generated by that.

Yes, you can simply copy/paste the code given by the page, no need to type it manually