Metallic Skins
There's a cool way to alter the "skins" of the athletes by entering specific city names in the name entry screen. You must be playing a game in Trial mode. There are several metallic colours to choose from, corresponding to the following chart:

Unlock New Events
You can unlock certain new events as follows (some events require you unlock other events first):

High jump and triple jump
Finish in the top 3 in the first 8 events in trial mode.

Pole vault
Place Gold in all 8 regular events and at least silver in the high jump and triple jump events.

You can skip the above if you enter L.A as your name in championship mode.

Trap shooting
Place gold in all 8 regular events and the 3 bonus events.

Cheats