The phrase "a multitude of small" is correct and usable in written English.
It can be used to describe a large number of small items, details, or aspects in various contexts, such as writing, discussions, or analyses.
Example: "The project was successful due to a multitude of small improvements made over time."
Alternatives: "a large number of small" or "many small".
The water also contained a multitude of small crustaceans as prey.
Robert Rauschenberg, the designer, has spattered the backdrop and costumes with a multitude of small, brightly colored dots.
Agriculture is hobbled by a multitude of small plots leased from the state that cannot support mechanisation.
There were the six cities just mentioned, no mid-size cities, and a multitude of small cities.
Yet chamber music can be played in a multitude of small spaces -- chambers, that is -- making it relatively easy for listeners to find a nearby concert.
The private sector of the economy consists partly of a multitude of small enterprises and partly of enterprises belonging to large French or international companies.
The luminance signal, as it occupies the channel, is actually concentrated in a multitude of small spectrum segments, by virtue of the periodicities associated with the scanning process.
One big reason is that some companies are dominated by a few big shareholders, while others are owned by a multitude of small investors.
The latter's tiny but well-informed garrisons put a dent in the insurgency with a multitude of small-scale swarming raids on terrorist cells.
Instead they ginned up a multitude of small-bore fixes to reduce the complexities of life, one at a time, in a rather Martha Stewart-esque fashion.
To the North, also the triangle underneath the two stretches of the Como Lake area is included in a pact ("Patto locale di sicurezza urbana dell'area Triangolo Lariano"), as the result of the institutional joint initiative of the Prefecture, the Province of Como, and a multitude of small-sized municipalities not exceeding 5000 inhabitantsu.
