Color BSD68 dataset for image denoising benchmarks It is part of The Berkeley Segmentation Dataset and Benchmark https://www2.eecs.berkeley.edu/Research/Projects/CS/vision/bsds/
This benchmark dataset is widely used for measuring image denoising algorithms performance, however I could not find it easily. It includes the original .jpg files, converted to lossless .png, and noisy with Additive White Gaussian Noise of different levels.
Authors: D. Martin and C. Fowlkes and D. Tal and J. Malik
Title: A Database of Human Segmented Natural Images and its Application to Evaluating Segmentation Algorithms and Measuring Ecological Statistics
Book Title: Proc. 8th Int'l Conf. Computer Vision Year: 2001 Month: July Volume: 2 Pages: 416--423