I am not Jehovah Witness follower but my Mother in Law is. She has recently lost her son. I was going to paint her a plaque that has the saying "Your wings were ready, but my Heart was not" with a feather that has doves coming out the end of the feather with her sons initials and date of birth and death at the bottom. I do not know if this is appropriate due to her religious beliefs. I want to do something nice for her and not offend her. So if I could please get some input from someone who could help me out it will be greatly appreciated.
I am one of Jehovah's Witnesses.
This sounds like a very nice gift. Expressing your condolences will be comforting to your mother-in-law, but a plaque such as this could also help her to feel better when she finds herself grieving again in the future.
As you may know, Jehovah's Witnesses don't believe that we become angels in heaven when we die. We believe he is asleep in death (see What Happens When You Die?). We do believe, however, that we will see our dead loved ones again in the resurrection on a Paradise earth (see What Hope Is There for the Dead?).
If possible, I would do some more research on a suitable scripture or phrase which would reflect the hopes of your mother-in-law, or even a personalized scripture that describes some positive attribute of her son. Remember that this should be comforting to your mother-in-law, and not bring back painful memories.
From personal experience, the scripture that comforts me most is Revelation 21:4:
4 And he will wipe out every tear from their eyes, and death will be no more, neither will mourning nor outcry nor pain be anymore. The former things have passed away.
Here is a brochure that should help you: When Someone You Love Dies.
You may also like this article with tips on gift-giving: The Quest for the Best Gift.
This JW website describes their belief about death.
What happens at death is no mystery to Jehovah, the Creator of the brain. He knows the truth, and in his Word, the Bible, he explains the condition of the dead. Its clear teaching is this: When a person dies, he ceases to exist. Death is the opposite of life. The dead do not see or hear or think. Not even one part of us survives the death of the body. We do not possess an immortal soul or spirit.
At some point in the future many will be resurrected, but for now they are not conscious in any way, according to JW beliefs.
The sentiment "your wings were ready" has connotations of becoming an angel in heaven, or perhaps flying away like a bird. Either way it does not accurately describe the JW understanding of what has happened to your brother-in-law.
This website is a mail-order site for sympathy cards including quotes from the New World translation of the Bible, some of which are rather long for a plaque, but show the kind of message regarded as appropriate to JWs.
They include these:
He will swallow up death forever
Lord Jehovah will wipe away the tears from all faces
I am the Resurrection and the Life
Looking forward to the happy day
and others, and there are other similar sites, which may give other ideas.
Whether your mother-in-law would be offended obviously depends on her, few persons take offence at the kind thoughts of others however expressed, but the idea that your brother-in-laws wings were ready for him is not strictly in accordance with the beliefs she adheres to.
NB I am not a witness myself, so hopefully one will come along and give a clearer and better argued answer than this.