What is the ruling on using images from the internet for the purpose of design and writing on them, editing them and publishing them, and writing one's name on them after editing, knowing that the owners of the images are unknown and there is no permission from them? Is it permissible to publish them on mixed social media platforms like Instagram? Is it permissible to publish artistic images of children or nature?

It is not permissible to use or republish images if it is highly probable that their owners would object. If the situation is unknown, the default is permissibility.

It is permissible to modify images such that they are attributed to you, provided there is no lying or falsification.

There is no harm in publishing images through the mentioned website if you are secure from temptation and corruption.

Hand-drawn images of children are not permissible, while photographic images are a matter of dispute among scholars.