Craft an abstract background for a marketing agency's landing page. Employ bold shapes and vibrant colors to evoke energy and creativity. Incorporate flowing lines and geometric elements to suggest fluidity and innovation. Experiment with gradients and contrasts to add depth and visual interest. Focus on creating a sense of movement and excitement that reflects the dynamic nature of marketing. Avoid text to allow the imagery to speak for itself, inviting visitors to engage with the agency's brand and services through visual intrigue and curiosity.