If your main priority for training is aesthetics (and it is for more of you than would like to admit) then you could do far worse than emulating the training of athletes in a sport whose body shapes you desire.
The thing you have to consider, that many people do not, is the volume, variety, intensity, and duration of the training these people do, and not just thinking of the event they compete in. Just because you desire a 100m runners body shape does not mean you should do lots of 100m sprints, as their training program is significantly different than this.
I believe a personal desire to achieve something – anything – will provide better motivation over the long term though, and so it is this I advise you ask yourself: Is there an event/race I have always wanted to do? Whether it is to walk ATB or run across Africa, swim 500m or the Cook Straight having a goal and a coach (and the training squad that the coach provides) will give you more motivation than wanting to look like Ian Thorpe or Amanda Beard I think.