Oh I see
Yes, I'm also pretty curious why some icons don't get accepted, and keen on finding out more.
But I'd say, it's better to find some icons that could be used as inventory items (from their size and properties), and then compare those that work, and those that don't work. This could result in finding the cause.
Experimenting with "strange" .ico files (usually not used anyway because of untypical size etc.) won't be helpful in my opinion to find the cause
If you have any "normal" inventory items as .ico files that don't work with AM, please send them to me as email.
For a systematic comparison, I need quite a few icons (several that work, several that don't get accepted). I really hope that we'll be able to discover why AM accepts some icons and not others, while all seem to have similar properties.