Changes to Trap was a general reshuffling of the islands. No islands were lost or changed, they've simply been moved to different places.
The large island at B4 that was so often a haven for the North team's carriers has been moved all of the way up to A0, all but removing it from play. Similarly, the carrier hiding spots for the south team, found at G7 & F7 have been moved to surround the north and south (respectively) of C-Cap. The islands around C-Cap have been spaced out a little more as well, with the addition of the small island from E4 joining them as well.
The brown doughnut island at C7 has found new use being dropped right in the middle of B-Cap. This provides an interesting change to the dynamics of early game play, where ships rushing the death-trap that was B-Cap now have some cover to hide behind. This also leads to some point blank range fighting. This also has the additional purpose of reducing long range fighting between A & C caps.
Trap in 0.5.4, looking over the small sandbar island at G4, facing north through B-cap. Note the ruined settlement and muted sky and water colours, bright though the lighting may be.
Trap in 0.5.5. The islands have been updated, with burned out trees and the settlements on fire and spread out. Wrecks of ships (freighters and destroyers) now litter the beaches. The perimeter of the large doughnut shaped island can be seen on the right, centered on cap B. Perhaps more interestingly from a cosmetic sense, there was a change in the lighting, increasing the contrast and making the ocean appear a much more vibrant blue.
The Atlantic also saw an island shuffle and again the move seemed to be provide extra cover in and around the center most cap. The two small islands flanking north and south of the big rock at C5 have wandered to provide a north-western bit of cover around B-Cap. Around A-Cap, the large northern island got rotated about 30' and slid over to the north-west corner of A. The island at H4 now covers B-Cap from the south-east.
Cosmetically, there are now settlements all over the islands which has changed their topography somewhat.
Atlantic in 5.4. None of the islands had any settlements on them.
Atlantic in 5.5. The skybox hasn't changed but the addition of new towns and castles on the islands has really given the map a bit of vitality. Unlike on Trap, there were only subtle changes to the lighting, though it remains close enough to be scarcely discerned. The three pictures here are all from around the same island at D/E7.