I was just in the other room putting on a border and cutting another. Originally, I was going to piece the border, or put the same fabrics in it. But, I want to "tone it down" so I found a nice grey and did a two inch border, now I'm adding the yellowish as a 3 inch border, but I think I'll put that on the top & bottom only so it'll be a little longer. It's super square right now. I thought then I could really quilt up that big area with black thread and it would look nice. I'm going to do a 4-5 inch black border...I think that'll look good. While I was putting on the grey, I thought it would really look good with grey on the back, so it looks like I'm thinking like you guys.
I'll post a picture when I make a little more progress.