Issues w thumbnail archive.

Apparently, you’ve switched to the archive shortcode instead?

If you still prefer the thumbnails, here’s how:

The thumbnails are culled from the thumbnail files your theme makes when you upload a post image (i.e. comic). WordPress will automatically make smaller copies for quicker loading, which is a joke considering it’s really bad at compressing them and some of the ‘smaller’ files actually exceed your comics’ filesize, but I digress. Anyway, I’ve just simulated such an archive on my site, and the older thumbnails are indeed cut off. I’ve changed the settings for thumbnails a while after launching the site, and the newer ones look fine. So maybe the same action will help you:

Find the “Edit site” menu (depending on your setup, it should be one of the top menu entries, or under network/sites*), go to “Settings”** and scroll for the Thumbnails W and Thumbnails H settings. I’ve changed mine from the defaiult 140×210 to 210×210 so it’ll size down the larger side to 210, whichever it is. If your pages are all the same aspect ratio, you can just find yoor own measures. Also, below the Thumbnail size settings there’s an empty field titled “Thumbnail crop”. If that isn’t empty in your settings, you may want to make it so. (Actually, now that I think about it, maybe that’s all you need to do.)

For the images you already uploaded, I’m afraid you’ll have to re-do those. Either by re-uploading the images from WP-admin or by replacing the thumbnail files with your own equally-named files via ftp.

As for the ordering, you can switch to Ascending checking “Get first in chapter instead?” in the thumbnail widget. And you can set the number of thumbnails to be displayed to be really high to make sure they’re all there. Just remember to update that number when you exceed it or the newer ones won’t show.

*) or more to the point: either /wp-admin/site-settings.php or /wp-admin/network/site-settings.php if you have a multisite network.
**) Unless the above url already took you there.