What hardware are you using? I recently finished a project myself and I'd like to do more with e-ink but the hardware "driver" that plugs into the pi costs as much as the e-ink display.
I find the costs to be reasonable, but I just bought a Waveshare e-ink ESP32 controller to try boosting battery life, since I don't need a fully fledged OS. All I'm doing on the frame is pulling an image from an URL or displaying a local image if the connection fails.
Currently I transmute some images (XKCD and NASA APOD) via a scheduled GitHub action into something fit for the various display sizes. An even more extreme approach would be to convert into the packed (4bpp for 7-colour E-ink) framebuffer format server-side. Less network efficient, but more predictable memory usage.
We’ve had JPEG support for a while, but I brought up a PNG decoder (Larry Bank’s PNGdec) recently(ish) and it’s a much better fit than JPEG for palette-based images. It uses a 32K sliding window, however, which can get spicy if you’re not careful.