How to replace some text with picture in RichTextBox without clipboard?

Question

Like the title says I want to replace text (ex. ":)") with a smile face. I used clipboard method, but sometimes (usually with Google Chrome) it throws exception called: System.Runtime.InteropServices.ExternalException.

After I read about it they say, it is caused by other program who is using clipboard. So how can I avoid it?

Code I'm using:

int ind = TekstiKast.Text.IndexOf(emote);
TekstiKast.Select(ind, emote.Length);
Clipboard.SetImage(new Bitmap((Image)emotions[emote],new Size(16,16)));
TekstiKast.Paste();