I find this a bit strange...

Do you find the product pictures as listed in the Marklin database could sometimes differ to the actual thing?

I noticed this first with 39120 E10.3. Maybe it's just me, but I find this the most noticable. If you try and compare the pic of 39120 in the database to its 'brothers', the 39121 or 26540, there seems to be lot of different details; boogies, roof, underside, even the frontal look seems different.
Than I look at 39120 photos posted here and on eBay - gosh, they actually do very much alike 39121... I'm hard pressed to see whether this is the same lok as pictured in database.

The second one that I noticed is with the 39891. This one is actually minor. If you look at the picture in the database - you'll see that it has a black panto. The actual model have red pantos - just like 39890 and 39893.

Is this because they are photographing a pre-production mould or something?

Anyone else notice anything like this?

Catalogue and database pictures show "hand samples" - sometimes they even buy models from the competition and paint them.
This may explain differences in trucks or other details.

I noticed pantograph differences with several models. I presume this is just a matter of cost saving: re-use the pantographs of an earlier model to reduce the different spare parts on stock ...
There is an era V class 151 loco that has the red pantographs of the green era IV model where the catalogue shows black pantographs (and the prototype has black single-arm pantographs).
I have a DR E 18 (forgot the number) where the pics in the catalogue and on the box show different pantographs than the loco actually has.

The 39120 probably shows a handmade model (based on whatever) while 39121 shows a handmade model based on 39120.