I'm going to post this again because I think it really is the easiest way to upload pictures to a FlyerTalk thread....and some newer people may not know this option exists.
Have two tabs open... one to the thread and one to open My FlyerTalk.
Go to 'My FlyerTalk" - on the left side of the page under Networking is a link for Pictures and Albums. Click that.
Then click Add Album and Title it.
Click on 'Click Here to Upload Pictures' (I resize pictures to 600 mgpixels first)
Upload your picture.
Then, in your album choose the picture you want to share.
Underneath the picture you will see 'Picture URL'
Copy the URL
On the thread page, choose Reply to Thread
Choose the little icon at the top that is yellow with mountains (Insert Image)
Paste the picture URL
Type any comments you would like to add to the post.
Post.
Voila! Your picture is posted.