I have been through this, unless you are in mass production the right decision comes down to considering time, costs, and results:
-textured clear acrylic plexiglass might work but will not look nice for long
-textured clear polycarbonate might work but is expensive and will not look nice for long
-thick etched / textured glass is likely your best bet, but glass can be awkward and it will wear smooth eventually if it does not break
-custom artwork HPL is likely going to be very expensive but could be very very very cool
-used playfields will require both opportunity and careful measurements
-thai foosball did sell ok playfields but were plain artwork, unknown mdf quality, international shipping on a large object
-making a solid color would be relatively easy, good mdf covered well with green formica, but those markings are really really important, and so is absolute flatness.
After all my options were deliberated, I ended up buying a tornado field. I'd suggest that unless you are manufaturing it is not worth the effort and expense of making or retrofitting a playfield. You will get at best, a mediocre surface for a hundred bucks and countless hours of effort.
Oh, to leave you with some hope...This guy came up with something:
http://stealthboy.com/foosball_build.html"Also, I needed to figure out the playfield surface. In order to closely reproduce the surface of a Tornado (which is non-smooth), our playfield is made of a base 3/4" inch particle board, a paper playfield, and then 1/8" Plexiglas roughed with 60-grit sandpaper, all sandwiched with a clear artists' spray mount adhesive. This gives it a nice, translucent look while giving the right texture for ball pinning. I drew our playfield using the Gimp. You can download the file here [780K XCF]. So, our playfield cost $29 instead of the $250 for a real Tornado top. It's all about the budget."