It has been a while since I’ve served up a fresh Impromptu theme, so here goes. I don’t think I’ll make this the default, however it is based on the default theme with a few minor changes. I’ll be adding this to the documentation as well, but here is the css:

.jqifade{ position: absolute; background-color: #333333; }
div.jqi{ width: 350px; font-family: Verdana, Geneva, Arial, Helvetica, sans-serif; position: absolute; background-color: #ffffff; font-size: 11px; text-align: left; border: solid 3px #e2e8e6; -moz-border-radius: 10px; -webkit-border-radius: 10px; padding: 7px; }
div.jqi .jqicontainer{ font-weight: bold; }
div.jqi .jqiclose{ position: absolute; top: 0; right: 0; width: 18px; cursor: default; text-align: center; padding: 2px 0 4px 0; color: #727876; font-weight: bold; background-color: #e2e8e6; -moz-border-radius-bottomLeft: 5px; -webkit-border-bottom-left-radius: 5px; border-left: solid 1px #e2e8e6; border-bottom: solid 1px #e2e8e6;  }
div.jqi .jqimessage{ padding: 10px; line-height: 20px; color: #444444; }
div.jqi .jqibuttons{ text-align: right; padding: 5px 0 5px 0; border: solid 1px #e2e8e6; background-color: #f2f8f6; }
div.jqi button{ padding: 3px 10px; margin: 0 10px; background-color: #2F6073; border: solid 1px #f4f4f4; color: #ffffff; font-weight: bold; font-size: 12px; }
div.jqi button:hover{ background-color: #728A8C; }
div.jqi button.jqidefaultbutton{ background-color: #BF5E26; }
.jqiwarning .jqi .jqibuttons{ background-color: #BF5E26; }

Also feel free to share your themes for Impromptu. There is always room for improvement!

I have added this theme to the docs as “Smooth” theme.