1920 * 1080 / 8 = 259200
That’s a lot of images! 
So you are drawing 8x8 px thumbnails? I guess then it would be good that the source images have that size too, unless you rotate them in which case it would be good that they are at least twice as large.
Another approach which I haven’t tried would be to load an image that already has such a grid of thumbnails and then you use image.copy() to copy little parts of that image on to the main screen. No idea if this is faster, but at least you would be working with just one (or a few) images instead of thousands of them. This technique is used in websites to avoid making tons of requests to the server to load tiny images.
One more advanced approach would be to draw lots of rectangles using the same texture() that contains all the thumbnails and then target different parts of that texture in different rectangles by setting the u, v coordinates in vertex().
What’s faster needs to be tested
ps. Did you try both P2D and JAVA2D?