Hi Totoetsasoeur,
You need to check which theme is used for slim here:
/etc/slim.conf
(search for line containing "current_theme", and see the propertie value on same line: your theme folder name: grep 'current_theme' /etc/slim.conf).

Then reach the folder of the current theme:
/usr/share/slim/themes/[folder name]/
You have three files herein:
- background.png : background color image file (repeated on whole screen if needed)
- panel.png : the graphical mention of SliTaz logo and prompt to log in
- slim.theme : ascii configuration file for the current theme, included font sizes

You need to be root to modify most of these files.
Regards,
--Babaorum

hey
Do you think it is possible to use a background jpeg, too?
I know, we don't like jpeg as much, but there are lots of nice images in jpeg out there...^^
thank you :)

@babaorum
Thanks. It works exactly as expected. :)

According to your advices, I edited the file slim.theme as root:

$ su
password
$
$ vi /usr/share/slim/themes/slitaz/slim.theme
$

And changed the following initial line from:

...
input_font              Vera:size=11:dpi=75
...

to new one:

... 
input_font              Vera:size=18:dpi=75
...

And now I get a nice readable login input. :)

Once again thank you.
Stephane