As far as length, don't force it. That's only going to water it down. Maybe try something where you look at two of your already existing RPs and think about how you could have possibly intertwined them into one longer RP that has more depth, twists, and turns within it. Try piecing together already existing, or largely completed works (as practice). The act of figuring out how to write the "paste" that connects them together will also help you in other areas in the future too. Before you know it, the point where you used to feel finished with your RP will only be the conclusion of chapter 1, or scene 1, or whatever.

For videos, here's one method:
Easy way to add a Youtube video. Just take the ending code of the video link, which is the part that comes AFTER the = sign.

For example, if this is your link
http://www.youtube.com/watch?v=iJAyhKc4-Y0
you're going to want to only take the part I put in red^
and then put that code between the youtube tags like this:
[noparse][/noparse]

The "live" result will appear like this:

and hopefully won't have a copyright strike against it by shitty WWE like this video does, LOL


Now, as for GIFs specifically, just find a GIF online and then put its URL in this code in place of the fake URL I made up here:
[noparse][img]http//fakeURLgif[/img][/noparse]