Nowhere in the Bible are angels feminine. If angels are messengers from God, why do these messengers always manifest themselves as masculine? Is it because they assume the gender of their Divine dispatcher?
As far as I know, angels are different beings from us as they do not procreate. Matthew 22:29,30 says:
Jesus replied, “You are in error because you do not know the Scriptures or the power of God. At the resurrection people will neither marry nor be given in marriage; they will be like the angels in heaven.
Because they do not procreate, gender really is irrelevant.
EDIT: I will add; I believe that in the Bible they take the shape of a man, but as in human shape. We know not if this is a female or male shape. Just like in the Garden of Eden:
So God created man in his own image, in the image of God created he him; male and female created he them.
So man can be used to refer to mankind, instead of just male.
Here are some thoughts I have had over the years:
God created man in his own image, but God is not material and so He may have used the design which he used to form the Angels as a blueprint for making man. His original creation was masculine (Adam) for which he may have used the Angels as a pattern. So then Man may have been created in God's image (body, Spirit and Soul) which has no Material form and in the pattern of the Angels. And then when He decided to create woman as a companion for man; Knowing all things and especially that woman would be deceived by Satan and then entice Adam to intentionally sin, and that her punishment was to be the bearing of children modified that pattern and created Eve.
Of course that is pure conjecture on my part and there are no Scriptures for me to cite, but there are some things that I believe God just didn't think we needed to know before we go to Glory.