I apologize for my inconsistencies-- I was trying to reformat the code to make it easier to understand. Below is my attempt to solve the problem by specifying different picture and trial types, but it is still not giving me exactly what I am looking for.
Within both the orientation and the test blocks, each face and each application only appears once, which is good. The error comes in these face-application pairings not repeating themselves across blocks. Thanks for your help...
<picture AcceptButton>
/items = ("Accept.jpg")
/ position = (75%,80%)
/size = (16%,16%)
</picture>
<picture RejectButton>
/items = ("Reject.jpg")
/ position = (25%,80%)
/size = (16%,16%)
</picture>
<picture accept_pics>
/ items = accept_pics
/ select = noreplace
</picture>
<picture reject_pics>
/ items = reject_pics
/ select = noreplace
</picture>
<picture white_pics>
/ items = white_pics
/ select = noreplace
</picture>
<picture black_pics>
/ items = black_pics
/ select = noreplace
</picture>
<item white_pics>
</item>
<item accept_pics>
</item>
<item black_pics>
</item>
<item reject_pics>
</item>
<counter setup_white_pics>
/ items = ("W1S.bmp", "W2S.bmp", "W3S.bmp", "W4S.bmp",
"W5S.bmp", "W6S.bmp", "W8S.bmp", "W9S.bmp",
"W11S.bmp", "W13S.bmp", "W19S.bmp", "W20S.bmp",
"W21S.bmp", "W23S.bmp", "W25S.bmp", "W26S.bmp",
"W28S.bmp", "W30S.bmp", "W31S.bmp", "W37S.bmp")
/ select = noreplace
/ selectionrate = trial
</counter>
<counter setup_black_pics>
/ items = ("B1S.bmp", "B2S.bmp", "B3S.bmp", "B4S.bmp",
"B5S.bmp", "B6S.bmp", "B8S.bmp", "B9S.bmp",
"B10S.bmp", "B12S.bmp", "B984S.bmp", "B985S.bmp",
"B986S.bmp", "B987S.bmp", "B988S.bmp", "B990S.bmp",
"B991S.bmp", "B993S.bmp", "B994S.bmp", "B997S.bmp")
/ select = noreplace
/ selectionrate = trial
</counter>
<counter setup_accept_pics>
/ items = ("App14_1Template.jpg", "App14_2Template.jpg", "App14_3Template.jpg", "App14_4Template.jpg",
"App14_5Template.jpg", "App14_6Template.jpg", "App14_7Template.jpg", "App14_8Template.jpg",
"App14_9Template.jpg", "App14_10Template.jpg", "App14_11Template.jpg", "App14_12Template.jpg",
"App14_13Template.jpg", "App14_14Template.jpg", "App14_15Template.jpg", "App14_16Template.jpg",
"App14_17Template.jpg", "App14_18Template.jpg", "App14_19Template.jpg", "App14_20Template.jpg")
/ select = noreplace
/ selectionrate = trial
</counter>
<counter setup_reject_pics>
/ items = ("App13_1Template.jpg", "App13_2Template.jpg", "App13_3Template.jpg", "App13_4Template.jpg",
"App13_5Template.jpg", "App13_6Template.jpg", "App13_7Template.jpg", "App13_8Template.jpg",
"App13_9Template.jpg", "App13_10Template.jpg", "App13_11Template.jpg", "App13_12Template.jpg",
"App13_13Template.jpg", "App13_14Template.jpg", "App13_15Template.jpg", "App13_16Template.jpg",
"App13_17Template.jpg", "App13_18Template.jpg", "App13_19Template.jpg", "App13_20Template.jpg")
/ select = noreplace
/ selectionrate = trial
</counter>
<trial setup_pairingsaw>
/ ontrialbegin = [item.white_pics.item=counter.setup_white_pics.selectedvalue]
/ ontrialbegin = [item.accept_pics.item=counter.setup_accept_pics.selectedvalue]
/ trialduration = 0
/ recorddata = false
</trial>
<trial setup_pairingsrw>
/ ontrialbegin = [item.white_pics.item=counter.setup_white_pics.selectedvalue]
/ ontrialbegin = [item.reject_pics.item=counter.setup_reject_pics.selectedvalue]
/ trialduration = 0
/ recorddata = false
</trial>
<trial setup_pairingsab>
/ ontrialbegin = [item.black_pics.item=counter.setup_black_pics.selectedvalue]
/ ontrialbegin = [item.accept_pics.item=counter.setup_accept_pics.selectedvalue]
/ trialduration = 0
/ recorddata = false
</trial>
<trial setup_pairingsrb>
/ ontrialbegin = [item.black_pics.item=counter.setup_black_pics.selectedvalue]
/ ontrialbegin = [item.reject_pics.item=counter.setup_reject_pics.selectedvalue]
/ trialduration = 0
/ recorddata = false
</trial>
<trial orientaw>
/ stimulusframes = [1=accept_pics,white_pics]
/timeout=500
</trial>
<trial orientrw>
/ stimulusframes = [1=reject_pics,white_pics]
/timeout=500
</trial>
<trial orientab>
/ stimulusframes = [1=accept_pics,black_pics]
/timeout=500
</trial>
<trial orientrb>
/ stimulusframes = [1=reject_pics,black_pics]
/timeout=500
</trial>
<trial testaw>
/ stimulusframes = [1=accept_pics,AcceptButton,RejectButton,white_pics]
/ correctresponse = (AcceptButton)
/ validresponse = (AcceptButton,RejectButton)
</trial>
<trial testrw>
/ stimulusframes = [1=reject_pics,AcceptButton,RejectButton,white_pics]
/ correctresponse = (RejectButton)
/ validresponse = (AcceptButton,RejectButton)
</trial>
<trial testab>
/ stimulusframes = [1=accept_pics,AcceptButton,RejectButton,black_pics]
/ correctresponse = (AcceptButton)
/ validresponse = (AcceptButton,RejectButton)
</trial>
<trial testrb>
/ stimulusframes = [1=reject_pics,AcceptButton,RejectButton,black_pics]
/ correctresponse = (RejectButton)
/ validresponse = (AcceptButton,RejectButton)
</trial>
<block pairings>
/ trials = [1-40=noreplace(setup_pairingsaw,setup_pairingsrw,setup_pairingsab,setup_pairingsrb)]
</block>
<block orient>
/ trials = [1-40=noreplace(orientaw,orientrw,orientab,orientrb)]
</block>
<block test>
/ trials = [1-40=noreplace(testaw,testrw,testab,testrb)]
</block>