I've tried using the "insert image" icon and copied/paste the URL for my image but it just posts an image of a torn picture icon and nothing else. I've tried using both google photos and Flickr and get the same results (Also have attempted to type it out manually but with no results)

What is the URL? If it doesn't have a url that ends in .jpg .png .gif etc that might be your problem.

Oops I think I stumbled on it; Mods, feel free to delete this thanks!

That is your problem. You need to turn it into a jpeg/jpg gif or png.

I use https://postimages.org/
It's got a lot of ads, but in-between em is a button to upload image. Then it has options for forum posting and it gives the url link