Like title says... I've put images in the default first album, and they do NOT show on the website.
Is that possible? If so, how?

P.S. I am using the nightly build - 1.4.3.5, fresh install, etc., because 1.4.4.8 kept giving me trouble while installing.

Images should be placed inside an album within the albums folder.
(albums/youralbum/image)

Within the albums folder you can create as many albums and subalbums as you like.

That I already know... My question was is it possible to put images in the first /album folder

No. But what exactly are you trying to achieve?

A simple no would've done it on the first place.
May I ask why though?

And I already posted TWICE what I am trying to "achieve" - have images in the first /album folder!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1

I.e. this as the default landing page of zenphoto:
http://i.imgur.com/P1P96BK.jpg

So what you really want is to have the gallery open with that album displayed?

That is certainly doable and has been accomplished by some of our users. It does require theme customization, though.

This is why fretzl asked what you wanted to do instead of just saying "NO". "NO" was the answer to the question you asked, but not the answer to "can I get this to happen."