I'll translate the two next parts as soon as possible...
I know two
that are going to be really happy about that, CrystalMSN and Aid
And a big thanks to vaksa who did the screenshot (english version)
Ok let's start
Before starting anything, your base
This forum has rules
So please use signatures that are no bigger than 250*50 pixels maximum
At the time I did this tuto those rules wheren't there yet
So here are few 250*50 pixels backgrounds:
mini-Log.png)


right click save as (png)


1/ How to resize an image, and keeping it ratio
insert the wanted image in the signature to resize it 
click on the rectangular marquee tool (keyboard shortcut : M)

Select the layers you are going to resize, then right click on it and select manual transform

click and drag an angle to resize it as wanted, at the same time click on shift, this will keep the ratio .

Then, when done, click on the rectangle selection tool
Select Apply, if you want to do some more change select Cancel, or Don't Apply to cancel everything,

This work with anything, tux, icons, any objects ...
You agree, nothing hard until now
2/ the text
Before you do anything download the Denmark font Here
to install it move it to the fonts folder
C:\Windows\Fonts\ (also accessible through the Control Panel)
So, select the horizontal type tool (keyboard shortcut : T)

click on the image where you want to write (precision isn't needed yet) (a new text layer is created)
Select the font : Denmark
The color of the text is not important at all
And the text size is up to you
about 55pt for the pseudo alone
otherwise 36-40pt for the pseudo if you want to add one or two lignes of text below, and about 16pt for those small lignes
Select Crisp for the smoothing
and center the text
all those options are in the menu bar

Type your text
double click like on the following screenshot, and not on the text

You should have somthing like that

Go on Drop Shadow (click on the word)
Still as on the screenshot
Shadow color:
R:140 G:140 B:168
#8C8CA8

Then like on the screenshot, still don't know the name in the english version
Do like on the screenshot
the color isn't important, because the value is 0%

Then like on the screenshot

And like on the screenshot

Click on the color setting, the colored bar..

click on the effect blue red yellow

double click on the small square (0%)
to set the color

change the color as:
R:218 G:217 B:234
#DAD9EA
same thing for the 2nd small square (placed at 50%)
R:192 G:192 B:219
#C0C0DB
and the third one (100%)
R:233 G:233 B:245
#E9E9F5
click once one the 2nd square (at 50%)

notice the small rhombus on each side

click once on the first one
the mouse should be a hand, not a arrow 
be aware that the undo command works here, ctrl+Z
type 80 as on the screenshot

same thing for the 2nd on e but type 40 instead
close that window, by selecting the OK button
Finally like on the screenshot

the color is
R:100 G:91 B:182
#645BB6
close that window, by selecting the OK button
to center the text on the signature (if you want it to be centered)
Put it in the wanted height
select the signature backgroud layer

then in the menu bar
Layer Menu / align the locked layer / horizontal center
You're Done !
You should have something like this (Hopefully )

If you have any questions feel free to ask
PS: Sorry but I have a French version of Photoshop, so I do not know the english version option names 