What if you put the texture mapped quad in its own file, give it an unofficial part header, and stick it in the <LDraw>/Unofficial/parts directory? Put the texture in <LDraw>/Unofficial/parts/textures.
Hopefully LPub3D isn't modifying official or unofficial parts.
Code:
0 Jaco's Super-Awesome Sticker
0 Name: sticker.dat
0 Author: Jaco van der Molen
0 !LDRAW_ORG Unofficial_Part
0 !TEXMAP START PLANAR -40 -20 -40 40 -20 -40 -40 60 -40 globe_west.png
4 4 -40 0 -20.5 40 0 -20.5 40 24 -20.5 -40 24 -20.5
0 !TEXMAP END
Hopefully LPub3D isn't modifying official or unofficial parts.