What I do is have Dropbox installed on my phone, desktop computer and iPad. Then I set things to automatically save screen shots to the Dropbox "screen shots" folder. That way, I always know where the screen shots are, and can delete them easily once uploaded or emailed.
With regard to iPad or iPhone devices (or Android), you should use the "Tapatalk" app. That allows you to upload/attach any type of photo/screen shot in your camera roll stored on the device. It's much easier to use Tapatalk on a mobile device than it is to use a browser on said device, because the experience is optimized via Tapatalk for that device.
That said, I always use a desktop browser for all administrative, management and other serious work when posting HOW-TOs or other posts involving lots of images or mixed images and text.
Also, most people have their mobile devices' cameras set to take very high resolution and physically large (pixel size) images. These tend to be outside the already generous parameters that this forum has for image file and pixel size. So, if you take photos via a mobile device, which a lot of people seem to tend to do, they MUST be re-sized so that they fit within the forum's image size policies.
Again, if you use Tapatalk to most images taken with a mobile device, the act of uploading them via Tapatalk will automatically resize the image(s) uploaded to dimensions/file size that comply with the forum policies.
Hope this helps.....
Cheers,
Gerry