Three Slack images this tool can make
Slack uses square images in three places that suit a letter or emoji icon. The workspace icon identifies your team in the workspace switcher when people belong to several workspaces. App and bot icons appear next to every message an integration posts. Custom emoji show up in messages and reactions.
Workspace and app icons are exported at 512 x 512. Custom emoji are exported at 128 x 128, the size Slack shows them, which also keeps the file small.
Designing for the workspace switcher
People who belong to several workspaces switch between them by icon. If every icon is a grey initial, they pick the wrong one. A distinct background colour does more than the letters: give the workspace a colour that the other workspaces your team uses do not.
For a bot or app, make the icon clearly different from your workspace icon, so readers can tell at a glance that a message came from an integration and not from a colleague. An emoji that hints at the job (a calendar for a scheduling bot, a bell for alerts) works well.
Workspace
Two-letter company initials on your brand colour
Alerts bot
🔔 on a dark background
Team emoji
A single bold letter, exported at 128 x 128
Using the same icon outside Slack
The PNG is a plain square, so it also works as a profile picture elsewhere. Most social platforms crop profile pictures to a circle rather than Slack's rounded square; check the circle preview before reusing it, and keep the letters centred.
SociaHive does not connect to Slack, but if your team also runs public accounts, a shared icon across them makes your company easier to recognise.