Does Lego Indiana Jones 2 contain any new content compared to Lego Indiana Jones 1?

Yes, if you loved the first game, you will certainly love the second game.

The first three movies all have completely new levels, including some lesser known scenes, for a total of 15 levels, 1 world of 5 levels for each movie (around the same size as the first game) The fourth movie also has 15 levels, spread over 3 worlds.

In addition to the basic levels, each level has an "alternate mode", which you can enter after you have beaten the level, and there are an additional 5 bonus levels in each world.

As a bonus, each world has one additional secret bonus level, only availble after you've beaten all additional and bonus levels in that world.

This brings us to a total of 96 levels spread over 6 worlds making it even bigger than LEGO Star Wars, The Complete Saga, which had 72 levels (not counting bonus levels, but including the free-roam mode.), and and there is no duplication between the two games.

In addition to all those new levels, you can also create your own custom levels, which you can play later (sadly, no sharing between systems)

So, they added the new movie, but they also "enhanced" the levels from the original three movies. If you loved the lego series, you'll probably like the enhancements almost as much as you'd like a new lego game.