A suggestion. Find some large images of what you like and copy them to your computer. Open them in Photoshop and resize them using the
bicubic soft preset.
Save the results as TIFFs. Copy them to a flash disk and get them printed at a print shop.
(Before doing that, you
could ask the print shop what colour profiles they prefer, eg, Adobe RGB 1998, sRGB, etc.
But they're likely to have Photoshop anyway and the profile can be converted from there.)
Of course, you could always modify the originals with different filters to remove grunge, crop edges, denoise, etc.
There is some software that specialises in resizing images and the results can be quite astonishing (eg, Photozoom Pro, Pefrect Resize 9, etc).
Enlarging images to big sizes on your own computer can tax it. Ideally you should have a fair chunk of RAM and a decent graphics card.
If not, it can take quite a while (depending on how big you want the final, printable result to be).
I found a couple of images and did some blow-ups (haven't printed them - just to give you some ideas).
And yes, I am fully aware of the **** in-**** out saying.
However, image enlargement algorithms have come a long way.
http://i.imgur.com/JIdQRn4.jpg
http://i.imgur.com/3qy8ARZ.jpg
http://i.imgur.com/0kluo6G.jpg
http://i.imgur.com/bgZKjGs.jpg