All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The Muslim should not wear such T-shirts even if outside the prayer if by wearing them one imitates the polytheists in general or their dissolute young men in particular, because wearing them in this case is included in the forbidden imitation.
Even if wearing such clothes is free from any imitation, they should not be worn in prayer because of the pictures on them, which is the image that includes a human face; a matter that is forbidden as it is an image of a living being; this is the opinion of many scholars. Shaykh ibn 'Uthaymeen said:
"With regard to the image representing the face and the top of the body, then the Hadeeth of Abu Hurayrah, which we referred to, indicates that the head must be cut and separated completely from the rest of the body, but when it is joined to the chest, it is nothing less than a man sitting, contrarily to when the head is completely separated from the body. It is for this reason that Imam Ahmad said: 'The image is the head.' whenever he wanted to blur the picture, he would scrape the head off. It was reported that Ibn ‘Abbaas said: 'The picture is the head, so if the head is cut, it is not a picture.' Therefore, one should be careful about this because some people are careless about this matter." [End of quote]
Drawing imaginary images of living beings is included in the general prohibition.
For more benefit, please refer to Fatwa 4371.
Allah knows best.