Well, if they were going to do the most distinctive logo/trade dress of every decade (excluding one-offs and suchlike), the 90s would be
the Electric Superman version, no question. And we know we're not getting that!
Outside of the Electric Superman issues, the occasional issue where they dropped the logo entirely (like the "Face Month" cover) and the odd other exception (like the Supergirl post-Death thing), the combination of the 1983 Superman logo with a smaller "in Action Comics" subtitle drawn loosely after the original Action Comics logo was the basic logo from #667 (1991) to #785 (2002) - they did redraw the "in Action Comics" a couple of times, but you'd probably need the logos side-by-side to notice. Which means that if they went for Action #775 for the 2000s trade dress, they'd have two very similar logos side-by-side. Of course, if they went for the revised original seen on #814-904 (the end of the series), it still wouldn't be completely distinctive...
Still, the result would almost have to be better than the 2000s cover of
Superman Unchained #1, whose differences basically amounted to "a slightly different #1" and the "DC Spin" rather than "DC Peel" logo - they didn't even change the fonts for "The New 52" or creator credits. The post-Rebirth "DC Universe" corner box is a much clearer difference.
Well,
Action #684 was the Action Comics issue of the Death arc. [Note the flying Superman in the corner box, which was replaced with a straight S-shield starting with the "Funeral for a Friend"
SuperGIRL in Action Comics issues and continued that way even after he was back]
Other than the "Big 'Superman', small 'in Action Comics'" logos, the only other "90s" option is the 1990-1991 curved logo. Which did get
one iconic issue...
Logo-wise, there's basically two options. The one that would fit a post-Crisis time period is the Todd Klein "
"Comics in the A's serif" version. The other alternative is the
1977-1986 John Workman one - but that latter one could end up on a 70s cover too, of course.
Well, the "two circles" run had them, basically,
go back to the original logo. Depending on how keen they are on recreations, they either do that or the Workman logo, I think. Before that is just further development of the 40s-70s look, so I'd probably fudge things and go Workman.
And no need to guess here, since Allred already put the full trade dress, including DC logo, Action logo and even CCA insignia, on the original art!
50s was pretty static. Slanted Action Comics logo in a box towards the top left (gradually, inconsistently getting straighter as the decade wore on), a blurb to the right of the logo (which varied in style most ) and insignias in the very top left and very top right.
Biggest change is that for most of the first half of the decade the DC logo was in the top right, and a corner box featuring Superman was in the top left (although sometimes there were two DC logos instead!); whereas in the latter half the Comics Code Authority came along and took the top right spot, and the DC logo went where the Superman headshot had previously been - here's
Action #200 vs.
Action #202 to show the difference.
IMO, the
Action #195 (1954) layout would be a good template for a "50s" cover.
Yeah, that's pretty clear.
If you're going "pulp", the 1997 Annuals (e.g.
Action Comics), did a better job of that than the "30s" Superman Unchained #1 cover. Although that had a leg up from the art - amongst other things, showing a 1939-ish Superman design with a triangular rather than pentagonal S-shield - which this one doesn't have!), it kinda takes a second or third glance to notice the differences apart from the price - they traced Joe Schuster's drawing of the logo from Superman #1, but the standard "UNCHAINED" kind of overrides that visually, and everything else is small or fades into the cover (the "75 years" and barcode don't help either, of course, TBF).
Of the covers we've seen, ultimately the 40s (Cho), 50s (Gibbons), 60s (Allred) and 2000s (Bermejo) ones absolutely nail their periods one way or another in the art. The 30s (Rude), 70s (Steranko) and 90s (Jurgens - although he's partially sabotaged by the colourist giving Lois black hair) are decent enough pieces, but they could all be average variants for any issue today (costume notwithstanding). If they work at all as "period", it's going to be thanks to the logo & trade dress.