Welcome to the funnest forum around:welcome:
You can attach photo's to a new post with the little paper clip looking thing in the top margin, I usually put the pics I want to post in a folder on my desktop and I reduce them in size, I use the medium setting or 1024 maximum size. You can also link to a photo hosting site like Photobucket or any number of sites. I have found it easier to use the link feature.
You can link directly to YouTube also.
Rear spring is not adjustable for height other than spring pre-load which will have an effect on the sag, so it will make a little difference in the ride height.
+ 1 on what Jerry has already stated, Tapatalk is brilliant for uploading pictures directly from your mobile phone. There was a recent issue with Tapatalk and I-Phone which I believe is now resolved.