I love this picture. The bride is beautiful and absolutely radiant, and one thing that kind of contributes to making her really stand out is the concrete wall. If you had a busy flowery background it might compete with the bride a little bit. I sometime get funny looks from people when they don’t understand why I I’d choose to shoot against a brick wall vs. a shrub or something.
You learn after a while that simple is sometimes so much better for a backgrounds because it will focus all the attention on the subject. Another very important ingredient is good light. I’d much prefer a simple background that had beautiful light, to a busier one with light that is unflattering. 