The word selfie does not in any way derive from I. The base word is simply self. The -ie suffix is simply a way to derive one noun from another.
Now, words derived without proper reference to the etymologies of their compounds do exist. Witness, as example, homophobia, which etymologically should mean “fear of self”. However, this works best when people don’t know where the parts come from. However, the origin of selfie is quite transparent, so selfue seems, to me, unlikely to take off. Also, opposite words with such similar sounds are rare in English.
Answers in the related question for the antonym of selfie suggest possibilities such as yousie and elsie, deriving from you and else. These might or might not catch on, but they are at least based something real, which cannot be said for selfue.
And besides, what is the antonym of selfie? A selfie is not simply a photo taken of oneself. Oxford Dictionaries gives,
A photograph that one has taken of oneself, typically one taken with a smartphone or webcam and shared via social media.
Similarly, WordSpy finds an early definition of the word which doesn’t even mention taking the photo yourself:
This is, as the kids would say, a “selfie,” a photo taken with the intent to post it to social media sites.
— Alexis Madrigal, The Atlantic, September 10, 2012
A photo taken by someone else would probably be called a portrait, which is assumed not to be a portrait of oneself unless it is called a self-portrait.