I'd like to preface this by saying it is not for personal gain, as I am far from, and do not anticipate ever hitting level 100.

Correct me if I'm wrong, but I believe the trophy value on the Casino God trophy is 10 -- similar to other trophies. This seems low to me given the effort required to achieve it.

Rather than simply increase its value, I believe it could be used to maintain some motivation for individuals after they've hit level 100. It would go something like this:

1) For anyone level 100 or less in possession of the trophy, it has T=10.

2) After that, make it so for every X levels over 100, if you own the trophy its value is higher by some increment. Let's say X is 10 and the increment is 1, then if you're level 110-119 then T= 11, at 120 T = 12, ... at level Y T=10 + (Y modulo 100)/10.

There can , of course, be a max value after which it doesn't matter how many levels you gain. It also makes it a truly unique trophy and achievement, as nothing else would share those mechanics.