You can always send additional documents to the Visa Office if you feel you forgot to add them when you submitted the application. If your application was missing a required document in your original submission, then they would have returned the whole package to you. Police clearance is a required document but it is not a document that shows whether your relationship is genuine or not.
After you send them the pictures, chat history/ phone history (e-mails, skype records, phone cards, cell phone statements etc.), you send them as additional supporting documents. (Make sure to write the file number and the UCI number of the applicant as a cover page and on outside of the envelope you sent). I do not suggest that you mention anything about the interview as this may raise suspicion. It is up-to them whether they may waive the interview at any point in the future. You can't request to withdraw. do not do that. After they put you in a interview queue, they may remove you from the queue (again that may not happen) if they think they want to.
Dear goodman36,
thank you very much for your self-explanatory message and/or information. So now, I am clear with what is going on my application. I have sent the missing documents, supposed to be required, to the Visa Office in Nairobi and waiting for their response. Anyway, I hope it will help the process fast and that my file will be completed very soon. Another question I want to ask you is if you know anything about security check. This might have been another possible reason why my file was put on the interview queue. Would you tell me about security check please? I mean how is it possible for them to clarify my background within a year or two? What and how they check? Will it take a long time to finish?
Stay blessed!