The 'in-processing' issue is a current bug, it seems, and it's been passed on to the guys with the wrenches...
Bootskins, Logons, and Wallpapers are all predominantly a single image and as such are comparatively simple to 'create' in skinning terms and are therefore moderated.
With walls it's about at best 1 in 5 is approved, with boots and logons the 'odds' are better....more like 50-50.
With boots it's usually an issue with 4-bit colour not all that flash for some images...too grainy.
With Logons it's mostly 'whose image is it?' or was it just the background or did the 'skinner' actually skin the logon panel, buttons, etc.
It's nothing new here at Wincustomize....this "not everything is accepted - policy". If you feel you really MUST have everything you ever create hosted and visible for all then the best avenue is to do as Citizen Phazonmaster has suggested....make your own site for them.
BTW...no-one 'shits on them', literally or otherwise. We have to, and do deal with them as evenly as possible.
A little respect/appreciation for the hours the admins/moderators put in wouldn't go astray.
Think of your typical 40 hour week that you 'might' work....then double it and add 20 and think 'for gratis'. That's what I do just to win your undying appreciation, and others much the same...