Hi Ace,
To post a picture here, it has to exist on a website somewhere ... and you just post the LINK to it here, same as you've been doing already. (This is why I say it's important to make sure that the other website gives permission to link to its pictures ... otherwise it's "stealing" their bandwidth, since it is a load on THEIR servers every time someone views the picture HERE.) If you want to post a picture of your OWN rather than one you find on another website, you'll have to put it up on a website first. There are many services that will give you a small "home page" website for free, so you could post a picture on your own website, then link to it here.
To access your registration from a different computer, just go the the Members page and "log on" with your user name and password. Same thing if two people want to register from the same computer -- each one can have their own registration, just be sure to "log off" and let the second person "log on" to be recognized.
As for animations, the only kind that can be posted are animated ".gif" files ... and these are posted exactly like other pictures, using the [IMG] and [/IMG] tags.
Greg