Besides the neon/cardinal tetra option there's a similar type, the glowlight tetra that's quite nice. All these types would be good with 8 to 10 in a shoal in a 100L/25G tank. One problem with neon/cardinals is that you need to wait six months from the time the tank is new before introducing them, so another really beautiful fish is the harlequin (Rasbora Heteromorpha) which will work well in a group of six and is one of the hardiest fish you can put in as a beginner - these fish are great in the initial stocking of the tank. Angels unfortunately really need 17 inches of height and I suspect that may be a little taller than your tank. Honey Gouramis though can be a really nice "centerpiece" fish in a tank your size.
All this talk of stocking is nice but of course the tank probably won't be ready for fish for a couple months if its new so there will be plenty of planning time. Have you been told of or begun to read up on the "Nitrogen Cycle" and "Fishless Cycling?" That's important to prepare the biological filtration portion of the filter. Until that's been qualified, it's not ready to support fish. We always like to ask beginners about this because there is so much mis-information that can come from the local fish shops (LFS).
~~waterdrop~~