I was going to do this myself and do pics but Have not gotten around to it. This is based on a "tool tip" I saw in a wood working mag....
(Keep in mind this is very work intesive but nice and custom...)
measure the tool box. Make a square frame that fits teh demensions. Lay the tools you want in a nice configuration. Put saran wrap over each tool. Spray expanding foam in the box. After it hardens cut off the overflow with a long kitchen knife. You now have a custom tool tray that fits exactly to the tools that you have. For a nice touch buy some of that Plati-Dip spray (home depot, next to HD racing dept.
)and spray your desired color over the foam. Need to add a tool? Just carefully cut ot the foam to the tool measurements and there ya go.
I am going to to this for the spare tire in the trunk. It will be a little more involved but worth it I think.
Feel free to tell me I'm a goof, but I think it will work. In the mag, the guy took one of those small socket sets that come in the metal/plastic cases, but have the cheesey-flimsy socket holder. He duct taped th tools in and turned it over in the case and sprayed to foam in. he cut off the excess, anit it looked and worked great.