I did contribute this on openwrt's wiki OpenWRT.

What was done to this router is added 2x USB ports and a SD Card reader throught the GPIO. Everything is explained in the above link.

wrt54gl

Temporary fixation for sd slot.

Sideview of sd slot.

The magic bga.

Overview of USB assembly with 5 volt regulator.

Another overview.

Love overviews

5 volt regulator, closeup.

SD slot and USB slots drilled out.

Backside

SD card and USB slots hotglued in place.

Wires for USB solderd and hotglued for stability.

Closeup of USB ports

Wires for the sd card

sd card wires again

USB slots mounted.