yeah, good question, Ricardo. I admit I didn't know the fsimtools service, but looking at the airline logos, from their look and size, it seems they are taken from the ServInfo pool. If you install ServInfo (a desktop application) it comes with an image folder full of common airline logos. There are even some logos of purely fictional VA's (the group we fall into). But since ServInfo wasn't updated in years, there is no way to get a new logo into the default logo pool.
In the case of Servinfo it's only possible to add a picture and text line to the configuration yourself, and it will look like this
If someone is interested in doing this, here's the logo:
(right click and save; put in ServInfo's "logos" folder; then edit "servinfo.dat" to add ACH as airline)
And the one for Lufthansa
where you can see it's probably the same as in your screenshots from fsimtools.
As far as I understood the fsimtools API, the picture files are stored on their server (Vatsim and Ivao do not provide any logos, for sure). So maybe we can send them the above picture and ask them to include it. I can try to do that.