I'm new to this place. I've been messing around trying to make my pictures transparent because I'm a loser and all I have is MSPaint and Gimp which I barely know how to work.
So here's my question.
Do you absolutely have to have a small image to upload in Pixel Joint? And upon clicking on the small image, will you immediately be directed to the entire image?

Like previews on dA right?

Transparency on the web is only possible through the .GIF format.  Unfortunately, MSPaint does not have the ability to save transparent .GIF images.  I've never used Gimp, but from the screenshots on it's site, it looks advanced enough to have a transparency feature.

And your notions about the previews is correct.  A 'detailed' image is the image that is displayed before someone clicks on it, and it can be at most 100x100 size.  There is a field to give a bigger version of the image if the size goes past 100x100, that is whats shown after someone clicks the smaller image to view the complete image.

leelo, I was kiddin.
You'll find several Gimp question on this topic (resources). I don't use it but often see a new Gimp question pop up.

yeah paint can do some amazing things despite the small amount of options it has.

dont spam

sometimes up to a month. {adjusted for lack of patience}

We're doing this in our own time. You can wait or leave.

So you go through them all one at a time?
Wow.
Well then I'll just practice more pixeling.

We have female staff members?

well, we have Bisque but she seems busy in other areas in her life outside of PJ.