Why most icons look wrong on a slide
Two things go wrong when an icon meets a deck. The first is the white rectangle: a JPG or a flattened PNG carries its background with it, so the moment your slide is anything other than white, the icon announces that it came from somewhere else. Every icon on Thridy is a transparent PNG, so it sits on a brand colour, a photograph or a dark theme exactly as it sits on white.
The second is resolution. Slides get projected, exported to PDF, printed on an A3 handout and screenshotted into an email, and an icon sized for a 24 pixel toolbar falls apart at every one of those. The download here is a high resolution master, so you can scale it up to fill a quarter of a slide and it stays sharp.
How to put one on a slide
Download the PNG, then in PowerPoint use Insert, Pictures, This Device. Do not paste it from a browser tab: pasting sometimes brings a screenshot rather than the file, and a screenshot has a background whether you wanted one or not.
Hold Shift while dragging a corner handle to keep the proportions. If the icon needs to sit on a dark slide and looks slightly heavy, use Picture Format, Corrections and lift the brightness a few percent rather than reaching for a different icon set.
In Google Slides the route is Insert, Image, Upload from computer, and everything else is the same. Both applications keep the transparency.
Keep one style across the whole deck
The single biggest improvement available to most decks is not a better icon, it is the same icon style on every slide. A deck that borrows from three icon sets reads as three different documents stapled together, and an audience notices before they can say why.
Everything on Thridy is rendered in one consistent 3D style with the same soft studio lighting and the same camera angle, which means a slide with four icons on it looks composed rather than collected. Pick a pack, use it for the whole deck, and the visual consistency comes free.
Colour, shadow and the export
A 3D icon already carries its own lighting and its own shadow, which means it does not want PowerPoint adding a second one. Turn off any shape effect the theme applies automatically, because a drop shadow under an object that is already lit produces two light sources and the eye reads it as a mistake without knowing why.
If you need an icon to sit tighter against a coloured panel, crop the transparent margin rather than scaling the icon down. Cropping changes how much empty space surrounds it; scaling changes how big the object looks next to everything else on the slide, and mixed apparent sizes are what make a row of icons look uneven even when the boxes are identical.
When the deck goes out as a PDF, export rather than print to PDF. Exporting keeps the images at their embedded resolution, while printing frequently downsamples them to 150 dots per inch and the depth in a 3D render is the first casualty.
