When I launch doom_complete.pk3 (from WadSmoosh 1.3) with GZDoom v.4.5.0, only the start menu has an actual widescreen asset from game_widescreen_gfx.pk3, but it's not even the correct WadSmoosh background- it's the doom 2 titlepic. Also, at the end of every level, Nash Muhandes's widescreen assets are supposed to appear but they don't... Am I doing something wrong or does WadSmoosh not support game_widescreen_gfx.pk3...?
Hmm, yeah it looks like game_widescreen_gfx.pk3 doesn't have a filter directory for wadsmoosh. I'll look into getting this fixed in official channels, in the meantime you can use this file I cobbled together quickly to assess the problem: http://vectorpoem.com/doom/wadsmoosh_widescreen.pk3