Believe you have a ticket created with us on this already. Someone from our team will be in contact soon.
Please create a ticket on themehouse.com as our team might be able to help you out with this project. You can do so here.
With the correct permissions, you are able to remove covers directly by navigating to one of your members profiles, click Cover, and click the Delete cover option within the Cover drop-down.
I am able to replicate the same thing as you are on my demo. I'll get it reported on our issue tracker.
I'd suggest browsing around to see if you might be able to find documentation on installing both of these that fit with your server hardware. I found one here for jpegoptim and one for pngguant here. I'd say it varies on what type of OS or hardware you are running currently. This part of our...
This is doable with the Backstretch functionality which is explained within our documentation here.
EDIT: This is also doable through the page background style property under Page Setup. If none of these property edits work you then I'd suggest using custom CSS.