(Not really a concern, just mentioning because I happened to run into it.)
PictView: CMYK JPEGs
Appears that PictView does not support CMYK JPEGs.
A sample can be found attached to this bug report, https://bugzilla.mozilla.org/show_bug.cgi?id=44781.
I'll assume this was also mentioned back here, PictView: JPEG - Podpora více subsampling metod, but the samples are no longer available.
PictView: CMYK JPEGs
PictView: CMYK JPEGs
WinXP Pro SP3 or Win7 x86 | SS 2.54