It would be better for you to paste the same pic which you have applied in the NEET application form.

Now as per the online information available, students were instructed to upload images in White/light background. So it would be better for you if you had do so on the application form. But as you haven't done it, then you can use the white background image and paste it. There will be no issues at all.

To know more about NEET Photo requirement visit:

https://medicine.careers360.com/articles/neet-photo-size-format-documents

I hope this helps.