Ok. I recently found these files in jacekowski's repo:
http://maemo.jacekowski.org/binary/nolo/ .

I've found out, that pics 1-2-3 are in a "secondary" image and represent the RD icon, logo, usb icon respectively. So, now i'm know, where is NOKIA picture located in secondary.

Then i've C&P HEX representation in Notepad++ and started analyse.

Here is my little screencast:

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It's impossible to change image entirely without disassembling NOLO binary.

+IRC log where jacekowski explained how to find location:
http://mg.pov.lt/maemo-irclog/%23mae...01-14.log.html