Its called the gallery entrence picture, you can see why.
What
you do is:
*Click on "fan art"
*Click on "send"
*Then on "continue"
This is where you send fan art. You will
notice things at the top:
*Click "my gallery options"
*Click "change my gallery entrence"
Now all your pictures
will come up.
There will be a thing that says something like:
Your gallery entrence picture has been changed. It may not appear
imediatly, though"
There you go. Easy as pie.
Same rules
aply to images, just under fan images instead of fan art.

It just happens, what do you mean exactly?

Once you send in fan art, one of your pictures shows up in
black and white with your user name on it.

Strawberry -> Go ahead and go to "Send to the Site", "Fan
Art", "Gallery Options", and then to "Request Gallery
Entrance Picture". ;]

And as to Fan Art Mods
making them, they aren't the only ones who do - Yupik and I
still do them. Which they are simple, as long as you follow
some simple rules.

It doesn't appear for me, Mighty.

Those are called "gallery entrance pictures" but, you don't
make them yourself.

Go to "fanart" and click
the send tab. Click continue. You should have options to
choose from. Click the "manage my gallery" Then requests to
change my gallery entrance picture.

How do they
make them. Well the fanart mods or fanart entrance maker makes them and they need a
pogram such as, photofiltre, photoshop, gimp and paintshop
pro. Any thing that is a image editing pogram.

It may take awhile for the fanart mods to change it.
( I used to make the entrance pics.) But, it does take a
few days. whenever the mods get to them.