You can choose the proper printing method and production process based on the
following rules: 

a. Inkjet printing : inkject printed big posters with backlit. Printed on photographic papers first, then paste
them to lenticular boards.

The suitable lenses: 

 40LPI:  up to 60cm x 80cm

 20LPI:  up to 3m x 1.5m(horizontal), 1.5m x 2m(vertical).

b. Offset printing: print directly on the back of the lenticular sheets.

The suitable lenses:

   75-200LPI: from bookmark to A3 size

The suitable sizes are inversely proportional to the values of the LPI.

Basically it depends on printing methods, applications as well as the dimension of the lenses you 
need. In general, thick lenses are more suitable for printing large format, long viewing distance 
applications. Thin lenses are more suitable for small, handheld products.