Guild Wars 2

Is there some place ingame where you can test out gear on your character to see how it looks?
Or a site with such a function?

I would like to know this so I can make a better choice for the body type of my character.

Can you change bodytype later ingame?

Go to a bank or crafting station, click on Wardrobe, and then you can preview every available armor and weapon skin in the game on your current character. There are also sites like gw2armorgallery that show what all the armor skin sets look like.

You can change your body type after character creation by buying a Total Makeover Kit. Those can also drop from Black Lion Chests.

Thanks for the answer.