In addition to some snow, a lot of images in these couple of packs aren't very sharp and seem to have been upscaled from smaller sources. Do consider whether it's worth cutting them @Castroman, because in a lot of cases, I don't think they're actually improvements.

I did not upscale any of them. Sometimes, when I cannot download the photo (because of quality or because the image is a background) I take a screenshot of the picture and try to work from there. Some of these pictures I added some “sharpness” to them to look better. Unfortunately, on my computer it looked great - but checking it now, some of them does not look as pretty as I wanted.

Regarding the snow: Some pictures I download does not come with a background - and I simply use it. When a picture has background I use the background remover available (remove.bg).

By upscaling I meant that when the cut is cropped, it may not have been in 250x250 and needed to be resized upwards to fit those dimensions. As a rule of thumb, if the image needs to be smart sharpened, it might already be an indication that it isn't necessarily of the necessary quality to warrant it being cut.

With regards to the final point, if the image you download has a transparent background, I would suggest to (a) put it through remove.bg anyway so that any existing snow is removed or at least reduced and (b) check whether it needs cleaning.