for example Kino has a awsome feature EXPORTING STILLS . Basically you can export every single frame of video that you have in the program to images (jpg, png). This is very useful for those who wants to edit(photomanipulate) the frames in an editor like cinepaint.
Kino has it, hope Kdenlive would have that to.

You can do this today. Create a new render profile with Group "Stills" Profile name "PNG" and Extension "png". In the parameters, enter only "vcodec=png aspect=%dar". Now, when you use it, you must put a '%06d' in the filename - you might put it at the end, but before the extension and separate it with a hyphen if you like.