when you type in a post, above there are buttons for you to type in a url or host an image from your computer. When you have a direct link to a picture, such as one hosted on imageshack or soemthing, you can type in the url and you'll end up with [img ] and [/img ] around it. minus the spaces.
Also, as for having animated sprays, there are several ways to do this, but generally, you need to convert the gif to an image sequence, then compile them together into a .vtf file was it? I forget, but I'm sure there are many tutorials on youtube and google if you search around a bit.
Here's a small thing on gamebanana that might help you a bit. Just look into it more yourself though <: www .gamebanana.com/tu ts/8784