What kind of insulation for inside of a freezer

[Ross]

The plain extruded styrofoam will snap the foil faced urethane will be more tolerant of abuse and be much easier to keep clean. This is a picture of the inside of my freezer door.

 

[RichH]

Take a good look at 'aerogel' its a very high R-rated insulation and performs 'almost' to the level of vacuum panels. Unlike the traditional 'foams' it doesnt need 'all the thickness' to be efficient. Expensive.
http://www.inhabitat.com/2010/02/11/exciting-advances-in-insulation-with-aerogel/
http://www.glacierbay.com/ultra-r.asp
..... all at about 10X the insulation efficiency of 'foams' ..... or another way of looking at it is you only need 1/10 the thickness to be equivalent to the 'foams'. Important if you carry foodstuffs in 'out of the way' places, as you want more food in there than taking up valuable space with (inedible) insulation materials.