Milestone 3 : Refined the CopyMarioToORAM routine and moved it inside of the NMI, now it works as designed. Also refactored the 'actor' data that drives the function; See sprMario, sprMario_x, sprMario_y. Now to draw a character all I need is this routine, and 3 arrays; one with tile indexes, and one each of x and y offsets for each of those tiles. Then I can draw the entire thing in the right way given an X,Y starting point.

defines.S

@@ -0,0 +1,6 @@
+playerx=$0010
+playery=$0011
+curSpriteAttrOffset=$0012
+curSpriteTileOffset=$0013
+curSpriteXOffset=$0014
+curSpriteYOffset=$0015

nesgame.S

@@ -8,6 +8,8 @@
   .inesmap 0		;; use mapper 0; NROM, no bank swapping
   .inesmir 1		;; background mirroring (we don't care for now)
 
+  .include "defines.S"
+	
 	;; For NESASM, we need to tell it where each bank begins.
 
   .bank 0
@@ -166,38 +168,58 @@ _MAIN_LoadPaletteLoop:
 	LDA #%00010000		;; turn on sprites, no more background color
 	STA $2001		;; Write to PPU Control Register 2
 	LDX #$0
-_MAIN_CopyMarioToOAM:
-	LDA sprMario, x
-	STA $0200, x
-	INX
-	CPX #$20
-	BNE _MAIN_CopyMarioToOAM
-	LDX #$0
-_MAIN_MoveMarioToPlayer_x:
-	LDA playerx
-	ADC $0203, x
-	STA $0203, x
-	INX
-	INX
-	INX
-	INX
-	CPX #$20
-	BNE _MAIN_MoveMarioToPlayer_x
-	LDX #$0
-_MAIN_MoveMarioToPlayer_y:
-	LDA playery
-	ADC $0200, x
-	STA $0200, x
-	INX
-	INX
-	INX
-	INX
-	CPX #$20
-	BNE _MAIN_MoveMarioToPlayer_y
+
+	LDA #$80
+	STA playerx
+	STA playery
+	LDA #$0
+	STA curSpriteAttrOffset
+	STA curSpriteTileOffset
+	STA curSpriteXOffset
+	STA curSpriteYOffset
 _MAIN_loop:
 	JMP _MAIN_loop	 	;; Loop forever
 
 NMI:
+	LDX #$0
+_NMI_CopyMarioToOAM:
+	LDA playery
+	LDY curSpriteYOffset
+	CLC
+	ADC sprMario_off_y, x
+	STA $0200, y
+	LDA #$4
+	ADC curSpriteYOffset
+	STA curSpriteYOffset
+
+	LDY curSpriteTileOffset
+	LDA sprMario, x
+	STA $0201, y
+	LDA #$4
+	CLC
+	ADC curSpriteTileOffset
+	STA curSpriteTileOffset
+
+	LDA #$00
+	LDY curSpriteAttrOffset
+	STA $0202, y
+	LDA #$4
+	CLC
+	ADC curSpriteAttrOffset
+	STA curSpriteAttrOffset
+	
+	LDA playerx
+	LDY curSpriteXOffset
+	ADC sprMario_off_x, x
+	STA $0203, y
+	LDA #$4
+	CLC
+	ADC curSpriteXOffset
+	STA curSpriteXOffset
+
+	INX
+	CPX #08
+	BNE _MAIN_CopyMarioToOAM
 	;; We need to copy all our OAM data to put sprites on screen during
 	;; vblank. $2003 is the PPU OAM address, so we're going to tell it
 	;; to pull OAM from $0200, and do a DMA transfer.
@@ -221,31 +243,12 @@ NMI:
 palette:
   .db $0F,$31,$32,$33,$0F,$35,$36,$37,$0F,$39,$3A,$3B,$0F,$3D,$3E,$0F
   .db $0F,$1C,$15,$14,$0F,$02,$38,$3C,$0F,$1C,$15,$14,$0F,$02,$38,$3C
-playerx:
-  .db $08
-playery:
-  .db $08
-curSprIndex:
-  .db $00
-	;; I put the OAM copy here instead of $0200 because I want to
-	;; allow me to initialize some basic sprite organizations (such as
-	;; mario standing) without having to do a bunch of pokes into my
-	;; OAM copy, because the only thing that ever actually changes is
-	;; the X and Y position. But I couldn't get the NMI copying to work
-	;; correctly when trying to set a bank to .org at $0200; I'm probably
-	;; just doing it wrong, but for now this works.
 sprMario:
-	;; each 4-byte pair goes directly into the OAM
-  .db $00,$00,$00		; mario top left Y,tile,attrs
-sprMario_x:
-  .db $00			; mario top left X
-  .db $00,$01,$00,$08		; mario top right
-  .db $08,$02,$00,$00		; mario middle left
-  .db $08,$03,$00,$08 		; mario middle right
-  .db $10,$04,$00,$00		; mario middle bottom left
-  .db $10,$05,$00,$08		; mario middle bottom right
-  .db $18,$06,$00,$00		; mario bottom left
-  .db $18,$07,$00,$08		; mario bottom right
+  .db $00,$01,$02,$03,$04,$05,$06,$07
+sprMario_off_x:
+  .db $00,$08,$00,$08,$00,$08,$00,$08
+sprMario_off_y:
+  .db $00,$00,$08,$08,$10,$10,$18,$18
 
   .bank 1
   .org $FFFA