Cockipt uses the SimpleImage library, which has multiple issues with transparent png and gif files. The problems occur due to inconsistent libgd versions in PHP builds (bundled or libgd). Instead of changing the webhoster or writing custom workarounds for each hoster, it would be great to repair the SimpleImage library instead.
After my tests with 4 different hosts, it seems to work with the bundled gd, but not if PHP is compiled with libgd.
This is my ugly collection entries view with wrong thumbnails (host with latest libgd 2.2.5):
I wrote a simple test so Cory LaViska has a base to work with and to eliminate these issues once and for all.
So - if you can spend 10 minutes of your lifetime - copy the test repo on your host and send me a screenshot of the results, please.