This site seems similar to PA now. On PA I got around the whole image size and everything by attaching links from the web. If you store your pictures online with something like Google photos, Imugr, Photobucket, Etc you can do that. You just open the image, right click it and "copy image address". It's important that it's the image's address and not "coppy image", or "save image as". If you're using Google Photos which has privacy settings, you first have to move the picture to a "public" album before others can see the image you share. You do this by creating an album and going to album settings ("more options") and opening "sharing options" and turn on the "Anyone with the link can see these photos" setting. To insert the link so it shows up as a picture on a thread you use the insert image button which is below the Bold button on the reply page of this site. Then simply paste the "image address" in the brackets.
The nice thing about doing it this way is 1) you can put images in the middle of your writing instead of them all being at the end like with the attachment. and 2) you don't have to resize the image. It can be whatever size it is in your storage site.