You will need to ensure you have several things showing in your screenshot.
- You need to have the server time/date in the upper left.
- You need to show the full Infinite Illusion interface.
- You need to show all three ii trials.

Did your screenshots have all of these conditions met?

If it is a size issue, I would recommend the following steps:

Resize your miniclient to be as small as possible when taking the screenshots. This should allow the entire interface to be viewable and make the screenshot small enough to be sent.
Use a compression tool to compress the screenshot (this may not work well, but is worth a shot).
Try saving as different filetypes. Some are bigger than others.

If all else fails, you can upload to an image hosting site such as imgur and submit the link, though be warned: fishy, unknown, or strange sites with weird links may not be opened for security reasons, so use a well known hosting site.