You kinda can - if you hit 'booster' or 'visual spoiler'; then choose to print from your browser.

There's some problems with getting them the right size; though.

You can, but I got to agree with Pierre... it's tricky. It's also tricky to print out an specific assortment of cards... say four of each common. Doable using the system we have? Definitely. Ideal? Not yet.

Hmm. I did already implement a "printer view" for details pages, deliberately to use them for proxy printing. For example, if you go to something like this details page, there's a subtle link at the top-right saying "Printable". Clicking that ought to take you to a page that's pretty good for printing proxies.

You can create details pages for any cardset you have edit permissions on. Inside them, include the card name in ((double round parentheses)) to embed the coloured card mockup. For example, this Testy details page comes out looking like this. So for example, on Ifreann, you can add details pages with the "Add details page" link in the grey box at the top of each Ifreann page.

Given all of which, I'm not sure there's very much more to do for this feature. Perhaps to let you select cards to print proxies of without having to make a details page first. That will come when I add the "decklist" feature, although that's not going to be very soon.

Actually, that makes sense. If you've got the ability to make decklists somewhere further down the queue, then that should take priority. My quibbles have more to do with organizing how you're going to print things, and decklists kind of solve 98% of the problem.