"Bride" is to "bridal" as "groom" is to …?

The OED has groomish but it's a nonce word with only one citation.

Interestingly, bridal wasn't formed from bride and the suffix -al. It was originally a noun bride ale, that is, "wedding feast". Since 1600 it was used as an adjective by association with words with the -al suffix, like nuptial, natal, mortal, etc.

Technically speaking I'm thinking the photos your niece took should be referred to as bridal on the basis that the online Merriam-Webster and Oxford Dictionaries refer to "bridal" as applying to both the bride AND the newly married couple. In addition, the Merriam Webster and the Canadian Oxford Dictionary also use the definition of "relating to a bride or a wedding".

I agree that there may be a need to coin a term that more specifically refers to the groom but in the context of your example such a term does not seem necessary.

http://www.merriam-webster.com/dictionary/bridal http://oxforddictionaries.com/definition/bridal