Endler's would be okay with shrimp or a frog. Small enough to be no threat to the shrimp, large and fast enough to avoid the frog, or anything else for that matter. I have dozens of male Endler's in a 55 gallon with a pair of breeding Angels, but they don't got eaten at all. However, the angels hunt down young Harlequin Rasboras relentlesly(which are small, but a bit bigger than the Endler's).
Espei Rasboras are smaller and slimmer than the Harlequins, but large enough to be appreciated...
Some of these micro-rasboras are a bit too small for me, can't hardly see 'em. You could have a school of 6-7 w/ shrimp or frog in a well maintained Spec V, it's a "large" tank for its size...
Celestial Pearl Danios are also tiny, but have a cool, perfect, tiny pattern...they look almost like a trout in extreme miniature. And do well with shrimp. They look really nice in a well planted tank with a dark substrate, and with all the different colored Neo shrimp. My LFS has a really nice 7 gallon display like this with CPDs a few species of micro rasboras, and a few different colored shrimp, reds, blues, yellows.
As for plants, if you're sticking with stock lighting, you'll probably want to stick with Java Fern, Mosses, Anubias nana or "petite. Also, small crypts would work, C. wendtii
. These plants together with some driftwood and rock will slowly fill in to form a thick jungle.
Some stems might also be possible with the stock light, but if you upgrade the lights, your options would increase, though ferts and/or CO2 might be needed with improved lighting.