White First Communion gloves are a symbol of purity. We want our hands to be clean and our hearts to be pure when we receive Jesus in the Blessed Sacrament. The gloves symbolize this. In the past, since people received the Eucharist ONLY on the tongue, gloves were common and hands were clasped in prayer, The gloves certainly are a way to complete the First Communion attire!
Check at your parish regarding the use of gloves during the ceremony. They will always be appropriate for great looking First Communion pictures!