After reading all replies and thinking about them I realized that I have unintentionally made some mistakes and also did not communicate clear enough. Because of the discussion about intel-cards and chinese clones I took inspiration from other certification marks and sigils. What I called a placeholder logo in my previous email should have been called a placeholder certification sigil. It is correct that a logo needs to be quite scalable and that too much text or text at all can be problematic especially when you need it rather small as an icon. On Wednesday I made some quick sketches and tests around the ideas to use a big capital "E" and somehow fill in the other letters. To get enough space I stretched the "E" and realized that I know an already existing logo working on the same principle: It is the logo of the Electronic Frontier Foundation that you can see here: https://www.eff.org/press/logos This can be a problem and I don't want the EOMA68 logo to look like a rip-off. Without stretching the "E" space inside the letter is quite limited. I also try to avoid designs where the letters "OMA" stand out too much because it means grandmother in german and german is my native language.
Today I decided to work with the base forms of the placeholder sigil -- blue circle and green circuit board. As requested I turned the card 90° counter-clockwise. I added a second circle and while testing another idea I coincidentally deformed the circle. I have to admit that I like the result very much. It still represents green earth and blue ocean but also an inserted computer card. You can see it here: https://www.parobalth.org/eoma-logo/EOMA68-base-form.png And with text underneath: https://www.parobalth.org/eoma-logo/EOMA68-base-form-text.png
I used a mono spaced font. It may also look good to use a VGA-font for the text as a reference to text-terminals and classic hackerdom but I could not find one already available for the graphical user interface.
Some thoughts to other mentioned ideas: I do not like the cat idea but maybe can be convinced by a clever designed cat logo. :) The idea about a dot in the "O" of EOMA made me think of fonts where the dot is in the 0 (zero) to distinguish it from O (capital letter O) As we all are somehow computer related I would find such a design confusing. I can not contribute to ideas with "proper historical reference to hacktivism and groups like anonymous" because I am not familiar with their conventions.
More to come...but not today. Goodnight!