IMO, I don’t think any requests are general, I think they are strategic and targeted. Okay, if they manage to get a holiday snap with his car then perhaps that’s useful but I think they are talking to specific people and making specific requests.
As an example, the recent photos of the three-finger CB selfie and the picture of him with the pixelated girl. I don’t know the source of the photos but they were released to German media, they don’t seem to have been picked up elsewhere and now I can’t find them online. I think it’s possible that these photos were released to inform CB and FF of information they have which was not collected at the box-factory but another source ... perhaps a more incriminating source, this may explain why FF has lost his media voice recently.
On the other requests, I think it’s likely they have photos of other victims and associates and exif data showing location and time and this is possibly May 2007. For some reason (Perhaps sunburn ) they suspect that these people are British ... they don’t have voice information or the accents would allow them to identify where to focus in the UK.
I just think that the investigation is at too late a stage, and let’s face it German LE is completely committed, to be making requests for random information - IMO they are nudging specific individuals to talk.