Praise be to Allah.
Images of animate beings that have been drawn by hand or three-dimensional images are haraam and are included in the texts which contain a warning of punishment for the image makers.
With regard to images made by machines, which are called photographic images, there is a difference of opinion among the scholars concerning them. What seems to us to be the correct ruling is that they come under the ruling on images that is mentioned above.
From the above, it may be known that it is not permissible to put the image of a child or any other animate being in e-mail or on chat rooms and the like. The prohibition is even more emphatic if the picture is of a female or if the picture is of a handsome man who is aiming to put it there to attract girls and women. Such actions are not permissible even according to those who allow photographs, because this usage causes obvious evil and corruption.
And Allah knows best.