Well, the artwork of Shigeo Koike who does much of the Hasegawa box art is available as prints:

Shigeo Koike website

Some of the recent work Adam Tooby has done for Airfix is available at -

http://www.finesthourart.com/

Lots of nice aviation art available here:

www.aviationarthangar.com

Years ago I used a product called "Decal-it". It looks like white glue and you paint/spread it thickly over art that is printed on paper and it will lift off the ink. You then take that decal and stick it to a piece of canvas or fake canvas and it looks like a painting.

I used art found in scifi/fantasy magazines by people like Freas, Bonestell, Frazetta, etc. It actually turns out pretty darn good.

The downside is the original art will be damaged/destroyed.

Also, the original artwork for box covers was alot smaller than one would expect.

With modern computer photo editing software, which many of us have, it is pretty easy to clean up and resize box art. You can clone over lettering and such.

When you scan the image, invoke halftone removal (or de-moire) filter.

...yes...

Don,

This would work too. I know you can buy printer paper that looks like canvas.

On a home computer most of us are going to be limited to standard or legal sized paper.

I suppose one could scan the box art  and try to get a local/online photo service to enlarge and print on special paper.  Walgreens is always running specials on photo print services. Photo enlargements seem to be very reasonable.

However, they may refuse to print it for you if they believe it violates copyright law. Which I'm pretty sure printing box art would.

https://www.google.com/search?q=john+steel+revell+art&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=S3X-T7uxDcfi2gWEu6m-BA&biw=980&bih=621&sei=f3X-T_TDIKrW2AWfzaHkBA