I second the lap idea. I found on accident (while toweling dd off one day in my lap) that'd she held still then. I'd bend one leg & put that leg's foot on my other knee and set her right in there--if that makes any sense. It really made a huge difference--the times I thought of doing it! My lo started getting crazy during changes (crying & everything!) at about the same time as yours, I think, and she just suddenly snapped out of it last week--right after talking to some other moms at a play area about the same thing! Makes me wonder if she caught on to what we were saying.
She's turning 15 mo. tomorrow. Now, she still cries and fights when I lay her down to change her, but then she holds still and we're done so fast!!! Oh, you can also try to make a game otu of it, that usually made it bearable. I literally had to "kiss her feet" to get her to let me change her.
I'd grab her feet and kiss the bottoms of them, switching between them rapidly, and giggle and tease her. That usually got her calmed down enough after I'd wiped her bum to let me get the diaper on--okay, well, at least one velcro tab done!!! New toys helped sometimes, but I think having her on my lap and having a game helped more consistently. Hope yours grows out of it faster than mine did!