Eshingyō (絵心経) are, as the name suggests, renditions in pictorial form of the Heart Sutra. They were invented during Edo's Genroku period, allegedly by a man named Zenpachi (善八), for the benefit of people (including priests) who couldn't read. Because the only thing better than a writing system based on thousands of stylized glyphs is a writing system based on a whole bunch of non-stylized glyphs, right? Seriously, Zenpachi, it's called an alphabet. Look into it.

Anyway, eshingyō work on the rebus principle. Take this example: the sutra's full* title 摩訶般若波羅蜜多心経, pronounced maka hannya haramitta shingyō in the Japanese reading, is represented thus:

• Pot (kama), upside-down → maka
• Nō hannya mask → hannya (yes, this one is totally cheating)
• Belly → hara
• Winnow (箕) →　mi
• Rice paddies (田) → ta
• Holy Shinto mirror (神鏡) → shingyō

Meanwhile, at the other end, that glorious gate, gate, pāragate, pārasaṁgate, or gyātei, gyātei, haragyātei, harasōgyātei in the Japanese pronunciation, has become:

• Monkey → monkey's cry → gyā
• Hand → te
• Monkey → gyā
• Hand → te
• Belly → hara
• Monkey → gyā
• Hand → te
• Belly → hara
• Priest → sō
• Monkey → gyā
• Hand → te

Sure, te should technically be lengthened, but I guess the idea is that the reader can do that him- or herself, much as they can add the gemination in /mitta/.

There are eshingyō all over the web, but this Tayama-style one and this Morioka-style variant are great places to start, being neatly drawn and including keys as they do.