I hate doing everything on a mobile device so if I need to add a photo to a post, I take the screenshot on the iPad (or take the photo of the iPad screen from my phone), let the photo sync up to <insert your cloud service of choice> and then back to my PC, where I can just drag and drop the image onto the post.
While on the topic, you can't attach videos. Best way to share a video with the community is to use a free service (imgur, YouTube, etc.) and share a link to the uploaded video.