There are a couple ways to skin a steel stand. My current tank is on a steel stand with plywood skin. The side panels are attached through the inside with screws through the steel posts. The front panel is attached using panel clips attached to 1x2 stringers spanning the front. This makes the front panel removable for easy access to the inside of the stand. Here are pics:
Panel clips attached to stand:
Clips on back of plywood panel:
Panel attached to front:
My new tank has a steel stand on a concrete pad. The panels are going to be attached to the sides, again using 1x2 stringers attached to the stand, and the screws through the back into the panels.
Work in progress still: