Yes, there was a "Otherworld Resort" DLC series with 3 maps released in Japan a few months after the game was out, as part of a second series of DLC.
There was a festival map, a beach one and a hot springs map. They're mostly focused on adding tons of extra support-like dialogue between the characters, 200 in total, but the second and third map also added 4 special illustrated scenes (2 men, 2 women in each map, based on a Japanese popularity ranking). They wear binikis or swimming trunks in the beach map and yukata in the hot springs one.
The Lucina art was just some art shown during the announcement of the second set of DLC, it isn't actually in the DLC. She gets a special scene in the hot springs map, so she's shown wearing a yukata, not a bikini. The characters with special scenes:
Beach - Chrom, Gaius, Tharja and Cordelia
Spa - Owain, Inigo, Lucina, Severa
In addition, the beach map has an 3d model swap effect on sorcerers, which get to wear trunks or bikinis there, while the hot springs map has the Swordmasters wearing yukatas.