Modern ones yes, but surely not the likes of these:
(Link to an image - not mine - of EMD E-unit diesels in Santa Fe Warbonnet livery)
If only some of the early modernisation plan locos could have looked like that!
The GM/EMD E & F ranges, the Baldwin Sharknoses (particularly the RF-16), the Fairbanks-Morse streamliners (Erie-Built & C-Liners) and the Alco PA/FA are the best looking of the early North American diesels and some of the best-looking period imho. The early streamliners couldn't be further removed from the likes of the GE U-Boats & EMD's GP7, SD40-2 etc. If you want a unhappy/ungainly looking American diesel from the early years, look no further than EMD's BL2.
For some time, I've been aware of
an incredible site (Railroad Picture Archives) stuffed full of old-school North American diesel pics (late 40s on), though my eye has fallen squarely on the Pennsylvania Railroad (following on from pics, given they operated streamliners from every major diesel loco builder in the mid-late 40s through to the early/mid 60s (GM/EMD, Alco, Baldwin & Fairbanks-Morse). These images - all part of the Thomas C. Ayers collection - best illustrate the latter three at work. While PRR Black is not the most photogenic livery (especially compared to those Santa-Fe EMDs!), the lines of these machines still manages to come through pretty well.
Fairbanks-Morse CF-16 (C-Liner): resembles a EMD if you were to squint, but it has enough of it's own distinct differences to set it apart.
Fairbanks-Morse FF-20 (Erie-Built): perhaps the fussiest/messiest of the bunch, in terms of the side-panels/grilles
Alco FA-1: a design classic in it's own right. While not terribly successful, Alco's offering is tied with the Baldwin Sharks in terms of aesthetics for me.
Baldwin RF-16 & BP-20 aka Sharks or Sharknoses: among the most attractive diesels ever to run state-side. Criminal that only two of these (RF-16s) survive today.
All 4 builders side-by-side in profile (more or less)
