Topsheets and graphics
Quotes are verbatim and attributed to their original authors.
The topsheet seals the top of the ski and carries the graphic. The main material choice is PBT versus nylon, and graphics are either ordered pre-sublimated, printed at home by dye-sublimation, or improvised from fabric and iron-on transfers.
PBT versus nylon
PBT is cheaper and takes sublimation well, but builders repeatedly complain it chips; nylon is tougher, lighter, and easier to wrap for cap construction, at the cost of fussier bonding:
Nylon rewards prep: flame-treat it just before layup and don't starve it of resin or over-press it. As the graphics supplier in that thread put it, poor nylon bonds usually trace to "too much pressure and/or not enough resin saturation… test test test."
Sublimated graphics
The easy route is to order sublimated topsheets from a shop such as CODA Boards (about $40 plus shipping, with fast turnaround), Miller Studio, or Snowboard Materials. To print your own, builders run a dye-sublimation setup — a wide-format Epson with Sawgrass inks, and a RIP program to handle large, complex images — then press the transfer into the topsheet:
Clear tops and cheap alternatives
A clear nylon topsheet over printed fabric, a fabric graphic, or the bare core is a popular look. On a budget, builders iron inkjet transfers onto fabric and cover it with clear topsheet, or skip a topsheet entirely and press against Mylar or release film for a shiny finish. One habit worth copying: "I now take off the protective film before I layup. If there's any wrinkles at all in it, the finished topsheet will show it" (powderho).