Installing Debian on the minicomputer "Shuttle DS437" (to use as a media / web / ftp server) resulted for me in a lot of searching. I suspect that a how-to might save some time for other beginning linux-ers. The howto may also be usable for other small mini systems that have no CDROM drive and non-standard NIC drivers.

Main puzzles:
1) how to install debian using an SD card instead of the CDROM
2) how to get the WLAN interface working (Realtek 8192c is not in the standard distro)
3) how to get the LAN working (Realtek 8111G drivers are not in the standard distro)

Main info sources are the Realtek website and READMEs (useful!) and the debian install website. The drivers might be non-free (I did not check their licenses).

1) gather everything needed
1. the DS437 with RAM and harddisk installed, a keyboard, mouse and monitor
2. a SD card sized 1.5 Gigabyte or larger. Important: back it up, this will be completely erased.
3. some working pc with internet connection
4. download unetbootin (available for several OSs)
5. download the correct debian image – finally the live install worked for me. I picked the debian-live-7.4-i386-gnome-desktop.iso via debian.org
6. download the Realtek 8111G driver from their site (r8168-8.038.00.tar.bz2 worked for me)
7. download the wlan driver file by using a search engine to find rtl8192cfwU_B.bin .
2) prepare the SD card
1. run unetbootlin, fill out the fields. choose 'debian / hd media and select the .iso file, select start. Now the sdcard is bootable.
2. create a directory “rtlwifi” under the sd card root directory
3. copy rtl8192cfwU_B.bin to the rtlwifi directory
4. copy the .tar.bz2 files to the root directory of the sd card
5. eject the card when done, and put it in the shuttle DS437
3) install debian
1. switch off DS437, insert SD card, switch on
2. follow instructions as far as possible
3. all network related parts of the installer will fail, choose:
“do not configure network at this time”
“no network mirror”
4. reboot, login into debian.
You should be able already now to use WLAN.
4) enable wired LAN by installing the drivers
1. plug the ethernet cable into the connector closest to the dc power input (=eth0, the other is eth1)
2. start a terminal (in case of the gnome 3 desktop: choose Activities / Applications / Terminal)
3. type su, enter the root password (that was entered during install)
4. copy the tar.bz2 file from the sdcard to /tmp
5. follow the instructions from the Realtek README file found in the .tar.bz2 (change version numbers where necessary). In short:
1. tar vjxf r8168-8.038.00.tar.bz2
2. cd r8168-8.038.00
3. ./autorun.sh
4. if networking is not yet available then see README file
5) update sources.list
To install/remove/update software packages using apt-get, you need to manually edit the /etc/apt/sources.list to point to a mirror like ftp.<country>.debian.org
1. sudo gedit sources.list
2. for inspiration, you might want to use the chinese Debian Sources List Generator
3. sudo apt-get update
6) READY

In case of limited Wifi reception: it should be possible to mount an external antenna using the two prepared holes in the back panel.

Did I miss something? Hope this helps. Let me know.