What is vexing you? File size limit? Keep them under 1mb. It's possible to post a big (in pixels) image to fill the viewers screen if you limit the number of colors in the image. Try converting the image to GIF format.
Issues with posting images from I pad or phone....... having resizing image first .... also difficult to post image in pm
I think that's why this Testing area gets traffic. "Posts a series of images" *PM's which piece is for sale* (In case anyone was wondering, there's noting wrong with that. There are Rules about who can, and how often WTS or WTT post can be placed. If two members discuss and do a sale or trade in PM, that's just fine and dandy!)
Since TSD is a privately owned website, the hosting cost money. Limiting file size uploads helps to keep the cost down. If you haven't yet - consider trying Tapatalk app on your smart phone? It will resize the photo for you.