I only have 3 graphing calculators and only paid $50 for them (the CASIO is borrowed and the TI-83+ was donated to me with a broken screen cable, and later I resold the TI-84+ for $40 so just $10 in total) but it took me a week to make this back in June 2020. Consider the procedure (the one I took, other are possible):

1. Download HQ meme template, paste into GIMP.
2. Crop/resize to display res (96x64 or 128x64), adjust brightness/contrast.
3. Create a color palette with 4 colors according to calc’s display capabilities (non-adjustable grayscale levels for TI, adjustable tones from white through orange to dark blue to murky green on the CASIO - only orange tones and the dark one are useful for faces so I dialed contrast of each way down).
4. Change the image to Indexed Mode with the corresponding color palette.
5. Check if all looks good (all colors used sufficiently & appropriately), if not, undo & repeat from step 2.
6. Copy image into LogoMotion (2002 graphics software).
7. For Casio:
8. • Change palette to: 0=white, 1=red, 2=blue, 3=dark green (out of the 16-color DOS pallette).
9. • Copy to MS Paint. (I did not know any other software that can do step 10 back then.)
10. • Save as 4-bit BMP.
11. • Use bmp2cat.exe to create a CASIO-compatible file. You could reverse-engineer the format and make your own converter but this is faster.
12. • Build a USB-2.5" adapter using an Arduino’s USB-TTL chip (with the ATmega processor removed or held in “RESET” state) and old headphones.
13. • Connect the calc to the PC.
14. • Using Device Manager, find out the COM port to use.
15. • Use CASIO’s FA-124 software to transfer the file.
16. • Press MENU→E to adjust the contrast on the calculator (lower for all colors to get skin tone optimised sepia).
17. • MENU→5 (GRAPH), SHIFT→MENU (SETUP), disable axes & coordinates.
18. • MENU→1 (RUN), SHIFT→F4→F1 (Cls), EXE, OPTN→F6→F6→F2→F2 (RclPic), [image number], EXE
19. For TI-8x Plus:
20. • Make 2 monochrome copies of the images - one containing the MSBitplane, one as the LSBitplane.
21. • Upload both of each image to img2cpp, convert with settings 96x64, horizontal bytes, invert colors enabled.
22. • Copy the resulting code into a text editor.
23. • Use the Find & Replace tool to remove line breaks within data, as well as 0x byte prefixes and , separators.
24. • Change everything to uppercase.
25. • Download the Axe Parser and the game SET from ticalc.org.
26. • Upload SETSRC and SETPIC to the Cemetech online editor.
27. • Change the amount of splashscreen data from 512 to 768 bytes (fullscreen) and offset to 0 (top of screen).
28. • Paste your edited data from the text editor into the Pic4A and Pic4B variables, MSBitplane first, LSBitplane second. Rename them accordingly - both in SETPIC and SETSRC of course.
29. • Alter the code to add 1-2 extra splashscreens into the game, including the getKey(0) function to wait for a key press. Add the new images as variables in SETPIC.
30. • Download both files back.
31. • For calc connection, rebuild the Arduino-CASIO converter to a TI-compatible one, or use any miniUSB cable (84 only) and then a calc-to-calc cable for 84-83 transfer using 2 2.5" jacks with swapped L/R (Tx/Rx). (Official cables are expensive!)
32. • Download Axe, SETSRC, SETPIC and GRAYLIB to the calculator’s archive.
33. • Run Axe, set your shell of choice and compile SETSRC.
34. • Archive the resulting SET program, if your shell supports auto-unarchiving of programs (like MirageOS). If not, copy it to the PC for backup.
35. • Run SET. If the screen turns blank and then turned off, an unknown error has occured (happens in unedited version of the game too). Contents of RAM are then corrupted and therefore deleted on the next startup. This is why the game needs to be archived to Flash or backed up on your PC’s drive! Keep retrying (holding ON at the right time helps) until the game actually starts and the splashscreens are displayed sequentially. The rest of the game may be broken as the “full circle” card graphics are invisible, but we’re doing it for the splashscreen anyway.
36. Repeat steps 26-35 for all other TI-8x Plus calcs you have.
37. Build a cardboard stand for each calculator.
38. Attach a polariser to your camera to make the LCDs stand out (this halves the brightness of everything but the displays. The CASIO has a vertical polariser, unlike the TIs, but that is OK since it is rotated into a “sitting position” anyway).
39. Arrange the scene in an improvised lightroom with a pillow, metal clothespins and the calcs on cardboard stands. Unless you have expensive even indoor lighting, a cloudy day is required. Camera must be on a tripod with fixed focus, exposure, aperture, ISO, WB etc.
40. Take all the pictures you need, moving the TIs you don’t have 5 of between the shots. To simplify the editing process, go from left to right and always move the left one 2 spaces to the right, change the displayed image and resleeve the calc into another cover (to look like 2 different units) without altering the position of the other calcs.
41. Take close-ups of all displays to compensate for the compact camera’s subpar optics.
42. Combine the shots in good image manipulation SW.
43. Clean up imperfections.
44. Change the sin⁻¹, cos⁻¹, tan⁻¹ button labels of the CASIO to your Reddit Lemmy username for a subtle yet readable watermark.