Something has always irked me about Proto Shield and I'm quite surprised that (from what I can see) it's never been brought up here. Looking at some official art of Proto Shield, you can see that the entirety of the shield has an outline.
(http://vignette1.wikia.nocookie.net/megaman/images/e/ef/Protomanprotoshield.png/revision/latest?cb=20110109090926)
Simply enough, 8BDM's Proto Shield only has it on one side, easy fix by just mirroring it to the other side as below,
(http://i.imgur.com/Fy7oK8Y.png)
EDIT :
Figured I would put the pointed shield update in the main post as well.
(http://i.imgur.com/7r6PgZV.png)
I think for that one it really depends on the source, in concept arts it's shown as round, just about any time it's being held by Proto Man it's shown as pointing, and when he throws it to Mega Man, it's round.
Concept Art:
(http://vignette4.wikia.nocookie.net/megaman/images/c/c0/R20BluesShield.png/revision/latest?cb=20130514172801)
Held By Proto:
(http://vignette2.wikia.nocookie.net/megaman/images/8/85/ProtoManMM8.jpg/revision/latest?cb=20110819052807)
Thrown To Mega:
(http://vignette1.wikia.nocookie.net/megaman/images/a/a8/Pssprite.png/revision/latest?cb=20110208043204)
In this case I'd say it wouldn't be too out of place for the shield to be pointed considering the pickup does give you Proto Man's buster as well. So with that in mind, updated this comparison image to include the pointed edges.
(http://i.imgur.com/7r6PgZV.png)
Proto Man is also interestingly enough based off of
(http://vignette2.wikia.nocookie.net/gundam/images/8/86/Char_Aznable_One_Year_War.jpg/revision/latest/scale-to-width-down/170?cb=20100401174631)
Char Aznable, and one of his most popular units from the original Gundam
(http://vignette2.wikia.nocookie.net/gundam/images/b/bd/Chargelgoogbeamrifle_0079.png/revision/latest/scale-to-width-down/640?cb=20160119024414)
the gelgoog, which is where Proto Man's shield got it's design from.
Even Sniper Joe (which is where Proto Man's design came from) is also based off
(http://vignette2.wikia.nocookie.net/gundam/images/9/9f/Gelgoogqu_0079.png/revision/latest/scale-to-width-down/640?cb=20160119024415)
the gelgoog, with
(http://vignette2.wikia.nocookie.net/gundam/images/5/52/Zaku_II.jpeg/revision/latest?cb=20101208232844)
the Zaku for color.
So yea his shield was inspired by a pointed version as well. And like Gumball said, his skin already uses the pointed version.
Simply enough, 8BDM's Proto Shield only has it on one side, easy fix by just mirroring it to the other side as below,
If you mean the back sprite, it doesn't have one so that you don't see your own protoshield AND the HUD protoshield.
Oh I see.
I tried the pointed shield in game. Looks a little bit too skinny. What do you think?
(http://i.imgur.com/Ko1NZKT.png)
The pointed shield looks fine to me, probably could move it closer to the center as GBT said, but that might end up making it slightly more different to block shots with. Though changing the shield's look does bring up a bit of an issue with the HUD, it becomes inconsistent. So with that, I quickly threw together these HUD sprites based off of an old HUD that OrangeMario made. These ones try to add a bit more of a point to the top of it, probably could be sharper though.
(http://i.imgur.com/sKvhyaC.png)